CN115215727A

CN115215727A - High-energy-efficiency preparation method of alkali metal alkoxide

Info

Publication number: CN115215727A
Application number: CN202210391601.4A
Authority: CN
Inventors: D·勒特格; S·赖曼; A·M·里克斯; N·保罗; M·施罗德; P·齐策维茨
Original assignee: Evonik Solutions Ltd
Current assignee: Evonik Operations GmbH
Priority date: 2021-04-16
Filing date: 2022-04-14
Publication date: 2022-10-21
Anticipated expiration: 2042-04-14
Also published as: AR125355A1; CN115215727B; US20220340508A1; US11661388B2; EP4074684A1; BR102022007029A2; JP7411710B2; JP2022164648A; KR20220143583A

Abstract

The invention relates to a method for producing sodium and/or potassium alkoxides by reactive distillation in a countercurrent manner. The alcohol is reacted with the corresponding alkali metal hydroxide in a countercurrent manner. The vapour comprising alcohol and water is separated into at least two rectification columns arranged in series. The energy of the vapor obtained in the first rectification is used to operate the second rectification. This particular energy integration, combined with the establishment of a certain pressure difference in the two rectification stages, makes it possible to satisfy a particularly large proportion of the energy required for rectification by means of electrical power and to save on heating steam.

Description

High-energy-efficiency preparation method of alkali metal alkoxide

Technical Field

The invention relates to a method for producing sodium and/or potassium alkoxides by reactive distillation in a countercurrent manner. The alcohol is reacted with the corresponding alkali metal hydroxide in a countercurrent manner. The vapour comprising alcohol and water is separated in at least two rectification columns arranged in series. The energy of the vapor obtained in the first rectification is used to operate the second rectification. This particular energy integration, combined with the establishment of a certain pressure difference in the two rectification stages, makes it possible to satisfy a particularly large proportion of the energy required for rectification by means of electrical power and to save on heating steam.

1. Background of the invention

The preparation of alkali metal alkoxides is an important industrial process.

Alkali metal alkoxides are used as strong bases in the synthesis of numerous chemicals, for example in the preparation of active ingredients for pharmaceuticals or agrochemicals. Alkali metal alkoxides are also used as catalysts in transesterification and amidation reactions.

Alkali metal alkoxide (MOR) is prepared by reactive distillation of alkali metal hydroxide (MOH) with alcohol (ROH) in a countercurrent distillation column, wherein the reaction water formed according to the following reaction <1> is removed together with the distillate.

For example, in US 2,877,274A, a process principle is disclosed by which an aqueous alkali metal hydroxide solution and gaseous methanol are operated in countercurrent in a rectification column. In WO 01/42178 A1, the process is described again in a largely unchanged form.

Similar processes, additionally employing an entrainer such as benzene, are disclosed in GB 377,631A and US 1,910,331A. The entrainer is used to separate water and water-soluble alcohols. In both patents, the condensate is subjected to a phase separation to separate out the water of reaction.

Accordingly, DE 96 89C describes a process for the continuous preparation of alkali metal alkoxides in a reaction column, in which a water-alcohol mixture taken off at the top of the column is condensed and then subjected to phase separation. The aqueous phase is discarded and the alcohol phase is returned to the top of the column together with fresh alcohol. EP 0 299 577 A2 describes a similar process, in which water is separated from the condensate by means of a membrane.

The alkali metal alkoxides of industrial importance are those of sodium and potassium, in particular the methoxides and ethoxides. Their synthesis is often described in the prior art, for example in EP 1 997 794 A1.

The synthesis of alkali metal alkoxides by reactive rectification described in the prior art generally produces a vapor comprising the alcohol employed and water. For economic reasons, it is advantageous to reuse the alcohol contained in the vapor as a reactant in the reactive distillation. Therefore, the vapour is generally fed to a rectification column and the alcohol present therein is separated (described, for example, in GB 737 453A and US 4,566,947A). The alcohol thus recovered is then supplied to the reactive distillation as, for example, a reactant. Alternatively or additionally, a portion of the alcohol vapour may be used to heat the rectification column (described in WO 2010/097318 A1). However, this requires compression of the vapor in order to achieve the temperature levels required to heat the rectification column. The vapor is cooled between compression stages, wherein the multistage compression is thermodynamically favorable and the intercooling ensures that the maximum permissible temperature of the compressor is not exceeded.

Heat integration within the rectification stage for efficient utilization of the energy used is described in different contexts of Ott, j., gronemann, v., pontzen, f., fiedler, e., grossmann, g., kersebohm, d.b., weiss, g., and Witte, c. (2012), methane.in Ullmann's Encyclopedia of Industrial Chemistry (editors). (doi: 10.1002/14356007.a16 \u465.pub 3). Paragraph 5.4 of this citation discloses the treatment of the crude methanol obtained in a conventional synthesis process by rectification using a plurality of rectification columns. It is generally proposed to utilize the heat of condensation of the vapours obtained at a rectification column at relatively high pressure for heating a rectification column at relatively low pressure. However, this citation does not disclose the relevant context of an advantageous energy integration in the separation of water-methanol vapor produced in the reactive distillation of alkali metal alkoxides.

In the preparation of alkali metal alkoxides, it is possible on an industrial scale, in particular in integrated plants (chemical, technical parks), to use heating steam as an energy source for meeting energy requirements. The steam is typically generated in excess in the integrated plant and can be utilized.

However, depending on the infrastructure and the energy available, heating steam is not always available, and in some cases, electricity is more cost effective. In these cases, there is a need for a process for preparing alkali metal alkoxides in which the lowest possible proportion of the energy requirement is met by heating steam and the highest possible proportion of the energy requirement can be met by electricity.

It is therefore an object of the present invention to provide an improved process for the preparation of sodium and potassium alkoxides by reactive distillation. The method should in particular allow a highly energy-efficient utilization of the heat released during the compression and cooling of the vapour. The method should also meet the highest possible proportion of energy demand by means of electricity as an external energy source and be characterized by the lowest possible heating steam demand.

2. Summary of the invention

Accordingly, the present invention provides a process for preparing at least one compound of formula M _A Process for alkali metal alkoxides of OR, where R is C ₁ To C ₆ A hydrocarbyl group, preferably methyl or ethyl, and wherein M _A Is selected from sodium, potassium, and wherein M _A Preferably sodium, wherein:

(a1) In the reaction rectifying tower RR _A At a pressure p _3A And temperature T _3A By passing a reactant stream S comprising ROH _AE1 And comprises M _A Reactant stream S of OH _AE2 In a counter-current manner to produce a catalyst comprising M _A OR, water, ROH, M _A Crude product RP of OH _A ，

Wherein in RR _A Is withdrawn at the lower end and contains ROH and M _A Bottom product stream S of OR _AP And in RR _A Withdrawing a vapor stream S comprising water and ROH at the upper end of (A) _AB ，

(a2) And optionally, simultaneously and spatially separately from step (a 1), in a reactive rectification column RR _B At a pressure p _3B And temperature T _3B By passing a reactant stream S comprising ROH _BE1 And comprises M _B Reactant stream S of OH _BE2 Reacting in a counter-current manner to produce a catalyst comprising M _B OR, water, ROH, M _B Crude product RP of OH _B Wherein M is _B Is selected from sodium, potassium, and wherein M _B Preferably the amount of potassium is such that,

wherein in RR _B Is withdrawn at the lower end and contains ROH and M _B Bottom product stream S of OR _BP And in RR _B Withdrawing a vapor stream S comprising water and ROH at the upper end of (A) _BB ，

(b) Passing said vapor stream S _AB And, if step (a 2) is carried out, the vapour stream S obtained _BB Is sent to a first rectifying tower RD ₁ In (2), the vapor stream S _BB And S _AB Mixed with or with S _AB The transfer is carried out separately from the other,

to be in said first rectifying tower RD ₁ To obtain a mixture G comprising water and ROH _RD1 ，

(c) In said first rectifying column RD ₁ At a pressure p ₁ And temperature T ₁ The mixture G is _RD1 Separated to be in RD ₁ Containing the vapor stream S of ROH at the upper end of (2) _RDB1 And in RD ₁ Of (2) a bottom stream S comprising water and ROH _RDS1 ，

(d) Passing said bottom stream S _RDS1 Is conveyed wholly or partially to a second rectification column RD ₂ In (1),

to be in said second rectifying column RD ₂ To obtain a mixture G comprising water and ROH _RD2 ，

(e) At a pressure p ₂ And temperature T ₂ Next, the mixture G is mixed _RD2 Separated to be in RD ₂ Of the top of (2) a vapor stream S comprising ROH _RDB2 And in RD ₂ A bottom stream S comprising water and optionally ROH at the lower end of (a) _RDS2 ，

Characterised in that p is ₁ >p ₂ ，p ₁ >p _3A And in the case where step (a 2) is performed, p ₁ >p _3B And wherein in addition preferably p _3A >p ₂ And in the case step (a 2) is carried out, it is furthermore preferred additionally that p _3B >p ₂ ，

And in that (f) will come from S _RDB1 To said firstTwo rectifying towers RD ₂ The mixture G of (1) _RD2 。

3. Description of the drawings

Fig. 1 shows a process according to the invention for preparing alkali metal alkoxides with corresponding interconnection of rectification columns.

Figure 2 shows a further process according to the invention for the preparation of alkali metal alkoxides.

FIG. 3 shows an embodiment of a process for preparing alkali metal alkoxides which is not in accordance with the invention with a corresponding interconnection of reactive rectification column and rectification column.

Fig. 4 shows a further embodiment of a process for preparing alkali metal alkoxides not according to the invention with corresponding interconnection of rectification columns.

3.1 FIG. 1

Fig. 1 shows a process according to the invention for preparing alkali metal alkoxides with corresponding interconnection of rectification columns. Adopt to be at p _3A Pressure of (2) a reactive distillation column ("reactive distillation column" hereinafter simply referred to as "reaction column") RR _A <3A>And are each at p ₁ And p ₂ Two rectification columns RD under pressure ₁ <1>And RD ₂ <2>. Herein, p is ₁ >p _3A >p ₂ 。

At RR _A <3A>Medium, naOH (stream S) _AE2 <3A02>) With methanol (stream S) _AE1 <3A01>) Reacting to produce a crude product RP comprising water, methanol, naOH and sodium methoxide _A <3A07>. At RR _A <3A>At the lower end of (2), the methanol-sodium methoxide mixture S is taken out _AP <3A04>. Reaction column RR _A <3A>Bottom evaporator VS at the lower end of _3A <3A06>For mixing the resulting mixture S _AP* <3A08>The concentration of the methanolic salt solution in (b) is adjusted to the desired value. In the reaction tower RR _A <3A>Can be additionally attached with a further evaporator, in particular for the reaction column RR _A <3A>An activated evaporator (not shown).

At RR _A <3A>As vapour stream S, a methanol-water mixture _AB <3A03>And (6) taking out. Will S _AB <3A03>Supplied to a first water/methanol column RD ₁ <1>Wherein optionally, in a reaction column RR _A <3A>S at the top of (1) _AB <3A03>In a condenser K _RRA <3A05>Partially condensed and recycled as reflux to the RR in liquid form _A <3A>Of the bottom plate. Then, at least a part of the vapor S is introduced _AB <3A03>Conveyed through a compressor VD ₃₁ <10>Thus introducing the vapor S _AB <3A03>Pressure of from p _3A To a pressure p ₁ 。

Thus, in the first rectifying column RD ₁ <1>To obtain a methanol/water mixture G _RD1 <108>. In the first water/methanol column RD ₁ <1>In (1), methanol is used as vapor S _RDB1 <101>And (5) distilling and recovering. Will be used as vapor stream S _RDB1 <101>Recovered methanol from RD ₁ <1>At the top of the discharge point<109>Is discharged and is partly in the rectifying column RD ₁ <1>Said stream S at the top of _RDB1 <101>In a condenser K _RD1 <102>Condensed and recycled to the RD as reflux in liquid form ₁ <1>Of the bottom plate. Will be used as steam S _RDB1 <101>The remaining part of the recovered methanol is depressurized to a pressure p ₃ E.g. via throttling D ₁₃ <11>And as methanol stream S _AE1 <3A01>Introduction into RR _A <3A>In (1).

In RD ₁ <1>Will comprise a bottom stream S of water and methanol (the other term for the lower end of the rectification column being "the bottom of the rectification column") _RDS1 <103>At the discharge point<110>And is discharged. Will flow S _RDS1 <103>First part S of _RDS11 <104>Supply to a second water/methanol column RD ₂ <2>Stream S _RDS1 <103>Second part S of _RDS12 <105>Recirculation to RD via bottom evaporator ₁ <1>VS in _RD1 <106>. Before being introduced into RD ₂ <2>Before neutralization, the step of adding S _RDS11 <104>Reduced pressureTo a pressure p ₂ E.g. via throttling D ₁₂ <12>。

Thus, in second rectifying column RD ₂ <2>To obtain a methanol/water mixture G _RD2 <206>. In the rectifying column RD ₂ <2>From S _RDS11 <104>Is separated from the water and is in RD ₂ <2>As a vapor stream S at the top of _RDB2 <201>Is distilled and recovered. Will be used as vapor stream S _RDB2 <201>Recovered methanol from RD ₂ <2>At the top of the discharge point<208>Is discharged and is partly in the rectifying column RD ₂ <2>At the top of the condenser K _RD2 <203>Condensed and recycled to the RD as reflux in liquid form ₂ <2>Of the bottom plate. As vapour S _RDB2 <201>The remaining part of the recovered methanol is passed through a compressor VD ₂₃ <13>Is thus compressed to a pressure p ₃ And from RD ₁ <1>Is reduced to a pressure p ₃ Of steam S _RDB1 <101>Together as a methanol stream S _AE1 <3A01>Is introduced into RR _A <3A>In (1).

In RD ₂ <2>A bottom stream S comprising water and optionally methanol _RDS2 <202>At the discharge point<207>And is discharged. Will S _RDS2 <202>S of _RDS22 <222>Partly via the bottom evaporator VS _RD2 <204>Is heated and recycled to the RD ₂ <2>In (1).

To heat via VS _RD2 <204>Recycled to RD ₂ <2>Partial bottom stream S in (1) _RDS2 <202>By using in a rectifying tower RD ₁ <1>Condenser K at the top of _RD1 <102>S in (1) _RDB1 <101>Energy released upon condensation. Recycling said energy to VS _RD2 <204>As indicated by the dotted arrow<4>Indicated. The energy supply can be effected indirectly, i.e. using S _RDB1 <101>And S _RDS2 <202>The heat transfer medium is a different medium from the heat transfer medium,or directly, i.e. by means of a condenser K _RD1 <102>Or bottom evaporator VS _RD2 <204>Middle messenger S _RDB1 <101>And S _RDS2 <202>And (4) contacting. In the case of direct contact, only the condenser K is used _RD1 <102>And omitting the bottom evaporator VS _RD2 Or only the bottom evaporator VS _RD2 <204>And omitting the condenser K _RD1 <102>Is sufficient, then in each case the stream S will be sent _RDB1 <101>And S _RDS2 <202>Both are conveyed through a condenser K _RD1 <102>Or bottom evaporator VS _RD2 <204>Such that energy, preferably thermal energy, is derived from S _RDB1 <101>Is transmitted to S _RDS2 <202>。

3.2 FIG. 2

Figure 2 shows a further process according to the invention for the preparation of alkali metal alkoxides. This process differs from the process shown in figure 1 in terms of the pressure in the respective column. In the embodiment shown in FIG. 1, p ₁ >p _3A >p ₂ And in the embodiment shown in FIG. 2, p ₁ >p ₂ >p _3A . This differential pressure regime enables the compressor VD ₂₃ <13>Not necessary, and attached, e.g., a throttle D ₂₃ <14>. Throttle D ₂₃ <14>Subjecting the vapor stream S _RDB2 <201>From p ₂ Reduced pressure to a pressure p _3A Whereas in the embodiment according to fig. 1 the compressor VD is ₂₃ <13>Making the steam flow S _RDB2 <201>From p ₂ To a pressure p _3A 。

3.3 FIG. 3

FIG. 3 shows an embodiment of a process for preparing alkali metal alkoxides which is not in accordance with the invention with a corresponding interconnection of reactive rectification column and rectification column. Similar to the embodiment described in FIGS. 1 and 2, the use of p is here made of _3A Pressure of (3) a reactive distillation column RR _A <3A>And each has p ₁ And p ₂ Two rectification columns RD of pressure ₁ <1>And RD ₂ <2>. Here, p ₂ >p ₁ >p _3A . The arrangement shown in fig. 3 corresponds to the arrangement shown in fig. 2 with the following exceptions:

1. intermediate evaporator VZ _RD1 <107>Arranged in a rectifying column RD ₁ <1>At, next to the bottom evaporator VS _RD1 <106>The intermediate evaporator VZ _RD1 <107>Can be used for steering RD ₁ <1>Mixture G of (1) _RD1 <108>The energy is supplied. For this purpose, mixture G _RD1 <108>At the discharge point<111>Is treated as stream S _RDX1 <112>From rectifying column RD ₁ <1>And (4) discharging. S _RDX1 <112>At VZ _RD1 <107>Is heated and recycled to the rectification column RD ₁ <1>In (1). In the embodiments according to examples 1 and 2, the corresponding intermediate evaporator can also be attached to the RD ₂ <2>。

2. Due to the rectifying tower RD ₁ <1>And RD ₂ <2>Of (b) is different pressure (p) ₂ >p ₁ ) Throttling D ₁₂ <12>By a pump P<15>And (4) replacing. The reason for this difference is that S is present according to the invention _RDS11 <104>Feeding into RD ₂ <2>Pressure of the stream inTo increase top ₂ 。

3. In an optionally present embodiment, additional methanol is used as stream S _XE1 <205>Through in rectifying column RD ₂ <2>To RD ₂ <2>。

4. In RD ₂ <2>S vapor at the top of _RDB2 <201>The energy released during condensation is passed via the intermediate evaporator VZ _RD1 <107>Is transmitted to S _RDX1 <112>And at S _RDX1 <112>Reintroducing into RD ₁ <1>After the second step, from S _RDX1 <112>To RD ₁ <1>Mixture G present in _RD1 <108>. Alternatively or additionally, RD ₂ <2>S at the top of _RDB2 <201>The energy released during condensation passes through the bottom evaporator VS _RD1 <106>Is passed to stream S _RDS1 <103>S of _RDS12 <105>And (4) part (a). At S _RDS12 <105>Recycled to RD ₁ <1>In this case, it transfers energy to the RD ₁ <1>Mixture G present in _RD1 <108>. Energy flow is indicated by the dashed arrows<4>Shown.

In the case of direct contact, only the condenser K is used _RD2 <203>And omitting the bottom evaporator VS _RD1 Or only the bottom evaporator VS _RD1 <106>And omit the condenser K _RD2 <203>Is sufficient, and then in each case the stream S is passed _RDB2 <201>And S _RDS12 <105>Both are conveyed through a condenser K _RD2 <203>Or bottom evaporator VS _RD1 <106>So that energy, preferably heat, is transferred from S _RDB2 <201>Is transmitted to S _RDS12 <105>。

3.4 FIG. 4

Fig. 4 shows a further embodiment of the process not according to the invention for preparing alkali metal alkoxides with corresponding interconnection of rectification columns. Similar to the embodiment described in FIGS. 1 and 2, the use of p is here made of _3A Pressure of (3) a reactive distillation column RR _A <3A>And each has p ₁ And p ₂ Two rectification columns RD of pressure ₁ <1>And RD ₂ <2>. Here, p ₂ >p _3A >p ₁ . Except for the pressure p _3A >p ₁ In addition, the arrangement shown in fig. 4 corresponds to the arrangement shown in fig. 3. This allows to connect the compressor VD ₃₁ <10>Omitting, using compressor VD ₁₃ <16>Alternative throttling D ₁₃ <11>。

4. Detailed description of the preferred embodiments

4.1 step (a 1) of the method of the invention

In the preparation of at least one compound of formula M _A In step (a 1) of the process according to the invention of alkali metal alcoholates of OR, in a reactive rectification column RR _A At a pressure p _3A And temperature T _3A Make the lower die compriseReactant stream S of ROH _AE1 And comprises M _A Reactant stream S of OH _AE2 In a counter-current manner to produce a catalyst comprising M _A OR, water, ROH, M _A Crude product RP of OH _A 。

According to the invention, a "reactive rectification column" is a rectification column in which the reaction of step (a 1) or step (a 2) of the process according to the invention is carried out at least in certain sections. It may also be referred to simply as "reaction column".

In step (a 1) of the method according to the invention, in RR _A Is withdrawn at the lower end and contains ROH and M _A Bottom product stream S of OR _AP . At RR _A Withdrawing a vapour stream S comprising water and ROH at the upper end thereof _AB 。

By "vapor stream" is meant that the corresponding stream is a gaseous stream.

In the process according to the invention, R is C ₁ -C ₆ The hydrocarbyl group is preferably selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, isomers of pentyl, e.g. n-pentyl, more preferably from methyl, ethyl, n-propyl, isopropyl, still more preferably from methyl, ethyl. R is particularly preferably methyl, and ROH is correspondingly methanol.

M _A Selected from sodium and potassium, preferably sodium.

Reaction stream S _AE1 Including ROH. In a preferred embodiment, based on the reaction stream S _AE1 Total mass of (S) _AE1 The mass fraction of ROH in (b) is 95 wt.% or more, even more preferably 99 wt.% or more, wherein additionally S _AE1 Particularly comprising water.

Used as reactant stream S in step (a 1) of the process of the present invention _AE1 The alcohol ROH of (A) may also be a commercially available alcohol which is reacted with the reactant stream S _AE1 Has a mass fraction of alcohol of more than 99.8% by weight and is based on the reactant stream S _AE1 Has a mass fraction of water of not more than 0.2% by weight.

Preferably introduced in vapor form into said reactant stream S _AE1 。

Reaction stream S _AE2 Comprising M _A And (5) OH. In a preferred embodiment, S _AE2 Not only contain M _A OH, and further comprises at least one additional compound selected from water, ROH. Except that M _A Outside OH, S _AE2 More preferably water, then in this case S _AE2 Is M _A An aqueous solution of OH.

When the reactant stream S _AE2 Comprising M _A OH and water, based on the reactant stream S _AE2 Total weight of (D), M _A The mass fraction of OH is in particular from 10 to 55 wt.%, preferably from 15 to 54 wt.%, more preferably from 30 to 53 wt.% and in particular preferably from 45 to 52 wt.%, most preferably 50 wt.%.

When the reactant stream S _AE2 Comprising M _A OH and ROH, based on the reactant stream S _AE2 Total weight of (D), M _A The mass fraction of OH is in particular from 10 to 55% by weight, preferably from 15 to 54% by weight, more preferably from 30 to 53% by weight and particularly preferably from 45 to 52% by weight.

In the reaction stream S _AE2 Except that M _A In the particular case where the OH group comprises both water and ROH, it is particularly preferred that it is based on the reactant stream S _AE2 Total weight of (D), M _A The mass fraction of OH is in particular from 10 to 55% by weight, preferably from 15 to 54% by weight, more preferably from 30 to 53% by weight and in particular from 45 to 52% by weight.

Step (a 1) of the process according to the invention is carried out in a reactive rectification column (or "reaction column") RR _A Is carried out in (1).

Step (a 2) of the process according to the invention is carried out in a reactive rectification column (or "reaction column") RR _B Is carried out in (1).

Reaction column RR _A /RR _B Preferably containing internals. Suitable internals are, for example, trays, structured packings or non-structured packings. When reaction tower RR _A /RR _B Where trays are included, bubble cap trays, float valve trays, tunnel trays, soman trays, cross-slit bubble cap trays or sieve plates are suitable. When reaction tower RR _A /RR _B Where trays are present, it is preferred to select trays that: wherein no more than 5 wt%, more preferably less than 1 wt% of the liquid trickles pass through the respective tray. Those skilled in the art are familiar with the construction measures required to minimize the dripping of liquids. In the case of float valve trays, a particularly tightly closed valve design is chosen, for example. Reducing the number of valves allows the vapor velocity in the tray openings to be increased to twice the value typically established. When using sieve plates, it is particularly advantageous to reduce the diameter of the tray openings while maintaining or even increasing the number of openings.

When structured or non-structured packing is used, structured packing is preferred in terms of uniform distribution of liquid. In this embodiment it is further preferred that the average ratio of liquid flow to vapour flow in terms of liquid does not exceed 15% or more, more preferably 3% or more, in all parts of the column cross-section corresponding to 2% or more of the total column cross-section. This minimized amount of liquid allows capillary effects at the screen to eliminate local peaks in the density of the liquid trickle.

For columns comprising non-structured packing, in particular random packing, and for columns comprising structured packing, the desired liquid distribution characteristics can be achieved when the liquid trickle density in the edge regions of the column cross-section adjacent to the column shell, corresponding to about 2% to 5% of the total column cross-section, is reduced by not more than 100%, preferably 5% to 15%, compared to the other cross-sectional regions. This can be easily achieved by e.g. the initial boiling point of the liquid distributors or the targeted distribution of their pores.

The process according to the invention can be carried out continuously or discontinuously. The process according to the invention is preferably carried out continuously.

According to the invention, "ROH-containing reactant stream S _AE1 And comprises M _A Reactant stream S of OH _AE2 The reaction in countercurrent mode "is achieved, in particular because: in step (a 1), a reactant stream S comprising at least a portion of the ROH _AE1 At a feed point of the reaction column RR _A Is comprised of M _A Reactant stream S of OH _AE2 Below the feed point ofAnd (4) preparing.

Reaction column RR _A Preferably in the reactant stream S _AE1 With the reactant stream S _AE2 Comprises at least 2, in particular 15 to 40 theoretical plates between the feed points of (a).

Reaction column RR _A Preferably as a complete stripper. Thus, in the reaction column RR _A Is supplied with a reactant stream S comprising ROH, in particular in vapour form _AE1 . Step (a 1) of the method according to the invention also includes the case where M is contained _A Reactant stream S of OH _AE2 But still in the reaction column RR below the feed point of _A Is fed in vapour form with a portion of the reactant stream S comprising ROH _AE1 . This makes it possible to reduce the reaction column RR _A The size of the lower region of (a). When in a reaction tower RR _A Is fed, in particular in vapour form, with a partial reactant stream S comprising ROH, in particular methanol _AE1 Then, in a reaction tower RR _A Is employed in a fraction of only 10 to 70 wt.%, preferably 30 to 50 wt.% (in each case based on the use as S in step (a 1)) _AE1 Of alcohol ROH) and contains M _A Reactant stream S of OH _AE2 Preferably 1 to 10 theoretical trays, particularly preferably 1 to 3 theoretical trays, the remainder being added in vapor form as a single stream or divided into a plurality of substreams.

Then according to the reaction described above<1>In the reaction tower RR _A In a reactant stream S comprising ROH _AE1 And comprises M _A Reactant stream S of OH _AE2 Reacting to produce M _A OR and H ₂ O, wherein these products react with the reactants ROH and M as a result of equilibrium reactions involved _A A mixture of OH's is present. Thus, in step (a 1) of the process according to the invention, in the reaction column RR _A To obtain a crude product RP _A The crude product RP _A Not only containing product M _A OR and water, and further contains ROH and M _A OH。

Obtain a mixture containing ROH and M _A Bottom of ORPartial product stream S _AP And in RR _A The lower end of the tube is taken out.

Vapor stream S previously described as "comprising water and ROH _AB "in RR _A Preferably at the RR _A Is withdrawn from the top of the column.

Preferably selected from the reactant stream S _AE1 The amount of alcohol ROH contained is such that the alcohol also acts as a bottom product stream S _AP Alkali metal alkoxide M obtained in (1) _A OR (ii) a solvent for OR. The reactant stream S is preferably selected _AE1 The amount of alcohol ROH in the reaction column RR _A As containing ROH and M, to achieve the desired concentration of alkali metal alkoxide solution _A Bottom product stream S of OR _AP Is taken out.

In a preferred embodiment of the process of the invention, in particular at S _AE2 Except that M _A In the case where the outside of the OH contains water, it is used as the reactant stream S in step (a 1) _AE1 Of the alcohol ROH and the total weight (mass; unit: kg) of the alcohol ROH used in step (a 1) as the reactant stream S _AE2 M of (A) _A The ratio of the total weight of OH (mass; unit: kg) is from 1 to 50, more preferably from 5 to 48, still more preferably from 9 to 35, still more preferably from 10 to 30, still more preferably from 1 to 1, most preferably from 13.

Operating the column RR with or without reflux, preferably without reflux _A 。

"without reflux" is understood to mean the RR _A A vapor stream S comprising water and ROH withdrawn at the upper end of (A) _AB Is completely supplied to the first rectification column RD according to step (b) ₁ . A vapor stream S comprising water and ROH _AB Preferably in vapor form, to first distillation column RD ₁ 。

"with reflux" is understood to mean the reaction column RR in the corresponding column, step (a 1) _A A vapor stream S comprising water and ROH withdrawn at the upper end of (A) _AB Is not completely discharged, i.e., is not completely supplied to first rectifying column RD in step (b) ₁ But rather at least partially, preferably partially, as reflux to the respectiveColumn, reaction column RR in step (a 1) _A . In the case where such reflux is established, the reflux ratio is preferably 0.05 to 0.99, more preferably 0.1 to 0.9, still more preferably 0.11 to 0.34, particularly preferably 0.14 to 0.27, and very particularly preferably 0.17 to 0.24. By passing a condenser K _RRA Attached to the respective column, reaction column RR in step (a 1) _A Can establish a reflux flow in the condenser K _RRA Medium vapor stream S _AB At least partially condensed and returned to the corresponding column, reaction column RR in step a 1) _A . In general and in the context of the present invention, a reflux ratio is understood to mean the ratio of the mass flow (kg/h) recycled to the respective column in liquid form (reflux) to the mass flow (kg/h) withdrawn from the respective column in liquid form (distillate) or in gaseous form (vapour).

In the reaction tower RR _A In the above embodiment in which a reflux is established, it is used as the reactant stream S in step (a 1) _AE2 Alcohol M of _A OH may also be at least partially, preferably partially, mixed with the refluxed stream and the mixture thus obtained is supplied to step (a 1).

In particular at a temperature T of from 25 ℃ to 200 ℃, preferably from 45 ℃ to 150 ℃, more preferably from 47 ℃ to 120 ℃, more preferably from 60 ℃ to 110 ℃ _3A Next, step (a 1) of the process according to the invention is carried out.

In particular at a pressure p of from 0.5 bar to 40 bar, preferably from 0.75 bar to 5 bar, more preferably from 1 bar to 2 bar, more preferably from 1 bar to 1.8 bar, still more preferably from 1.1 bar to 1.6 bar _3A Next, step (a 1) of the method according to the present invention is performed. The essential feature of the invention is that when the pressure p is established _3A The method comprises the following steps: p is a radical of ₁ >p _3A . In particular also p _3A >p ₂ 。

In a preferred embodiment, the reaction column RR _A Comprising at least one evaporator, in particular selected from the group consisting of the intermediate evaporators VZ _3A And bottom evaporator VS _3A . Reaction column RR _A Particularly preferably at least one bottom evaporator VS _3A . The evaporator is a special embodiment of the heat exchanger WT.

Condenser K is likewise a special embodiment of heat exchanger WT. Typical condensers are known to those skilled in the art. These condensers preferably serve as liquefiers at the top of the rectification column and the reaction column. In the direct energy transfer from the top stream of one column to the bottom stream or intermediate stream of the other column, the condenser of one column can simultaneously serve as the evaporator of the other column (as shown in the examples).

According to the invention, the "intermediate evaporator" VZ (e.g. RR) _A VZ in (1) _3A 、RR _B VZ in (1) _3B 、 RD ₁ VZ in (1) _RD1 、RD ₂ VZ in (1) _RD2 ) Is understood to mean arranged above the bottom of the respective column, in particular the reaction column RR _A /RR _B Above the bottom of or in the rectification column RD ₁ Or RD ₂ Above the bottom of the evaporator. They especially make the crude product RP as a side stream _A /RP _B Or S _RDX1Z And (4) evaporating.

According to the invention, the "bottom evaporator" VS (e.g. in RR) _A VS of _3A In RR _B VS of _3B In RD ₁ At VS _RD1 In RD ₂ VS of _RD2 ) Is understood to mean the heating of the bottom of the corresponding column, in particular of the reaction column RR _A /RR _B Or rectifying column RD ₁ Or RD ₂ The bottom evaporator of (2). They make a bottom product stream (e.g. S) _AP /S _BP Or S _RDX1S ) And (4) evaporating.

The vaporizer (vapourizer) is usually arranged outside the respective reaction column or rectification column. The mixture to be vaporized in the vaporizer is discharged from the column via a discharge opening (offtake) or "discharge point" (offtake point) and fed to the at least one vaporizer.

The vaporized mixture, optionally with a residual proportion of liquid, is recycled back to the respective column via a feed inlet (feed) or "feed point". When the evaporator is an intermediate evaporator, the outlet (takeoff) via which the respective mixture is taken off and supplied to the evaporator is a sidestream outlet, and the feed opening via which the respective mixture after evaporation is fed back to the column is a sidestream feed opening. When the evaporator is a bottom evaporator, i.e. a heated column bottom, at least a portion of the bottom output stream is evaporated and recycled to the respective column in the bottom region.

Alternatively, however, it is also possible to use, for example, an intermediate evaporator on a suitable tray or to provide tubes through which the relevant heating medium passes in the bottom of the respective column. In this case, vaporization occurs on a tray or in the bottom region of the column. However, it is preferred to arrange the vaporizer outside the respective column.

Suitable evaporators which can be used as intermediate evaporators and bottom evaporators include, for example, natural circulation evaporators, forced circulation evaporators with reduced pressure, steam boilers, falling film evaporators or thin film evaporators. The heat exchangers usually employed for the vaporizers in the case of natural circulation vaporizers and forced circulation vaporizers are shell-and-tube or plate apparatuses. When a shell-and-tube exchanger is used, the heating medium can flow through the tubes while the mixture to be evaporated flows around the tubes, or the heating medium can flow around the tubes while the mixture to be evaporated flows through the tubes. In the case of falling-film evaporators, the mixture to be vaporized is generally introduced as a thin film on the inside of a tube and the tube is heated externally. In contrast to falling-film evaporators, thin-film evaporators additionally comprise a rotor with wipers which distribute the liquid to be evaporated over the inner wall of the tubes to form a thin film.

In addition to the evaporator types listed, any desired further evaporator types known to the person skilled in the art and suitable for use on rectification columns can be used.

When reaction tower RR _A Reaction column RR _B Involving an intermediate evaporator VZ _3A Or VZ _3B When it is preferred to arrange the corresponding intermediate evaporator in the reactant stream S _AE1 In the region of the feed point of (3) in the reaction column RR _A In the stripping zone of (3), or in the reaction column RR _B Is arranged in the reactant stream S _BE1 In the region of the feed point of (a). This enables to pass through the intermediate evaporator VZ _3A /VZ _3B Can be introduced intoPart of the thermal energy. Thus, more than 80% of the energy can be introduced, for example, via an intermediate vaporizer. According to the invention, the intermediate evaporator VZ is preferably arranged and/or configured _3A /VZ _3B So that the intermediate evaporator introduces more than 50%, in particular more than 75%, of the total energy required for the reactive rectification.

When reaction tower RR _A Reaction column RR _B With intermediate evaporator VZ _3A Or VZ _3B It is additionally advantageous to arrange the intermediate evaporator such that the reaction column RR is _A /RR _B There are from 1 to 50 theoretical trays below the intermediate evaporator and from 1 to 200 theoretical trays above the intermediate evaporator. Particular preference is given to the reaction column RR _A /RR _B There are 2 to 10 theoretical trays below the intermediate evaporator and 20 to 50 theoretical trays above the intermediate evaporator.

When reaction tower RR _A Reaction column RR _B Involving an intermediate evaporator VZ _3A /VZ _3B It is also advantageous when the crude product RP is _A /RP _B Is supplied to the intermediate evaporator VZ _3A /VZ _3B Side stream outlet (i.e., reaction column RR) via _A At "output point E _RRA "/reaction column RR _B At "output point E _RRB "), and the crude product RP after evaporation _A /RP _B From the intermediate evaporator VZ _3A /VZ _3B Is sent back to the corresponding reaction tower RR _A /RR _B Side stream feed port (i.e., reaction column RR) whereby _A "feed point Z of _RRA "/reaction column RR _B "feed point Z of _RRB ") is positioned in the reaction column RR _A Reaction column RR _B Between identical trays. However, it is also possible to arrange the side stream outlet and the side stream feed inlet at different heights.

In a preferred embodiment, when in RR _A /RR _B In the use of an intermediate evaporator VZ _3A /VZ _3B Time, intermediate evaporator VZ _3A /VZ _3B Upper reaction column RR _A /RR _B Is larger than the intermediate evaporator VZ _3A /VZ _3B Lower reaction column RR _A /RR _B Of (c) is measured. This has the advantage of allowing savings in capital expenditure.

In such intermediate evaporator VZ _3A /VZ _3B Middle, reaction tower RR _A Containing M present in _A OR, water, ROH, M _A Liquid crude product RP of OH _A Or reaction column RR _B Containing M present in _B OR, water, ROH, M _B Liquid crude product RP of OH _B Can be converted into the gaseous state and, if already in the gaseous state, is further heated, thus improving the efficiency of the reaction of steps (a 1)/(a 2) in the process of the invention.

In the reaction tower RR _A In the upper region of which one or more intermediate evaporators VZ are arranged _3A Or in the reaction column RR _B Is arranged with one or more intermediate evaporators VZ _3B So that the reaction tower RR can be reduced _A /RR _B In the lower region of (a). In having at least one, preferably two or more intermediate evaporators VZ _3A /VZ _3B In the embodiment of (1), it is also possible to carry out the reaction in the reaction column RR _A /RR _B Is supplied in liquid form with a sub-stream of ROH.

According to the invention, the bottom evaporator is arranged in the reaction column RR _A /RR _B And is therefore called "VS _3A "and" VS _3B ". Can mix reaction tower RR _A /RR _B Bottom product stream S present in _AP /S _BP Is conveyed to such a bottom evaporator and ROH is at least partially removed therefrom to obtain a product with S _AP Compared with M having an improved mass fraction _A Bottom product stream S of OR _AP* To obtain a reaction with S _BP Compared with M having an improved mass fraction _B Bottom product stream S of OR _BP* 。

In step (a 1) of the process according to the invention, in the reaction column RR _A Is withdrawn at the lower end and contains ROH and M _A Bottom product stream S of OR _AP 。

Preferably, the reaction column RR _A Comprising at least one bottom evaporator VS _3A Then the bottom product stream S _AP At least partiallyIs passed through the evaporator to at least partially remove ROH, thereby producing a vapor with S _AP Compared with M with improved mass fraction _A Bottom product stream S of OR _AP* 。

With a bottom product stream S _AP M in (1) _A Mass fraction of OR, bottom product stream S _AP* M in (1) _A The mass fraction of OR is increased in particular by at least 1%, preferably by at least 2%, more preferably by at least 5%, still more preferably by at least 10%, still more preferably by at least 20%, still more preferably by at least 30%, still more preferably by at least 40%, still more preferably by at least 50%, still more preferably by at least 100%, still more preferably by at least 150%.

Preferably, when S is used _AP Or if at least one bottom evaporator VS is used _3A Wherein the bottom product stream S is _AP At least partially passing through the at least one bottom evaporator VS _3A To at least partially remove ROH, then based on S in each case _AP /S _AP* Total mass of (S) _AP* M in ROH having a mass fraction of 1 to 50 wt. -%, preferably 5 to 32 wt. -%, more preferably 15 to 32 wt. -%, most preferably 30 to 32 wt. -% _A OR。

Based on S _AP /S _AP* Total mass of (S) _AP /S _AP* The mass fraction of residual water in (a) is preferably<1% by weight, preferably<0.1% by weight, more preferably<0.01 wt%.

Based on S _AP /S _AP* Total mass of (S) _AP /S _AP* Reactant M in (1) _A The mass fraction of OH is preferably<1% by weight, preferably<0.1% by weight, more preferably<0.01 wt%.

4.2 step (a 2) (optional) of the process of the invention

According to the invention, step (a 2) is or is not carried out. In an optional step (a 2) carried out simultaneously and spatially separately with step (a 1) of the process according to the invention, in the reactive rectification column RR _B At a pressure p _3B And temperature T _3B By passing a reactant stream S comprising ROH _BE1 And comprises M _B Reactant stream S of OH _BE2 Reacting in a counter-current manner to produce a catalyst comprising M _B OR, water, ROH, M _B Crude product mixture RP of OH _B 。

In the optional step (a 2) of the process according to the invention, in RR _B Is taken out of the lower end of the vessel and contains ROH and M _B Bottom product stream S of OR _BP . At RR _B Withdrawing a vapour stream S comprising water and ROH from the top _BB 。

M _B Selected from sodium, potassium, and preferably potassium.

Reaction stream S _BE1 Including ROH. In a preferred embodiment, based on the reactant stream S _BE1 Total mass of (S) _BE1 The mass fraction of ROH in (b) is 95 wt.% or more, still more preferably 99 wt.% or more, with S additionally _BE1 Particularly comprising water.

Used as reactant stream S in the optionally present step (a 2) of the process of the invention _BE1 The alcohol ROH of (A) may also be a commercial alcohol which is reacted with the reactant stream S _BE1 Has a mass fraction of alcohol of more than 99.8% by weight and is based on the reactant stream S _BE1 Has a mass proportion of water of not more than 0.2% by weight.

The reactant stream S is preferably introduced in vapor form _BE1 。

Reaction stream S _BE2 Comprising M _B And (5) OH. In a preferred embodiment, S _BE2 Not only contain M _B OH, and further comprises at least one additional compound selected from water, ROH. Even more preferably in addition to M _B OH other than S _BE2 Also contains water, thereby making S _BE2 To be M _B An aqueous solution of OH.

When the reactant stream S _BE2 Comprising M _B OH and water, based on the reactant stream S _BE2 Total weight of (D), M _B The mass fraction of OH is in particular from 10 to 55% by weight, preferably from 15 to 54% by weight, more preferably from 30 to 53% by weight and particularly preferably from 45 to 52% by weightWt%, most preferably 50 wt%.

When the reactant stream S _BE2 Comprising M _B OH and ROH, based on the reactant stream S _BE2 Total weight of (D), M _B The mass fraction of OH is in particular from 10 to 55% by weight, preferably from 15 to 54% by weight, more preferably from 30 to 53% by weight and particularly preferably from 45 to 52% by weight.

In the reaction stream S _BE2 Except for M _B In the particular case where both water and ROH are contained in addition to OH, particular preference is given to those based on the reactant stream S _BE2 Total weight of (D), M _B The mass fraction of OH is in particular from 10 to 55% by weight, preferably from 15 to 54% by weight, more preferably from 30 to 53% by weight and particularly preferably from 45 to 52% by weight.

In a reactive distillation column (or "reaction column") RR _B In step (a 2) of the process according to the invention. Reaction column RR _B The preferred embodiment of (a) is described in section 4.1.

According to the invention, "ROH-containing reactant stream S _BE1 And comprises M _B Reactant stream S of OH _BE2 The reaction in countercurrent "is achieved in particular because: in an optional step (a 2), for a reactant stream S comprising at least a portion of the ROH _BE1 Is arranged in the reaction column RR _B Is comprised of M _B Reactant stream S of OH _BE2 Below the feed point of (a).

Reaction column RR _B Preferably in the reactant stream S _BE1 With the reactant stream S _BE2 Comprises at least 2, in particular 15 to 40 theoretical trays between the feed points of (a).

Reaction column RR _B Preferably operated as a complete stripper. Thus, in the reaction column RR _B Is supplied with a reactant stream S comprising ROH, in particular in vapour form _BE1 . The optional step (a 2) of the process of the invention also covers the following cases: in the presence of an alkaline solution M _B Reactant stream S of OH _BE2 Below the feed point of (a) but in the reaction column RR _B Into the upper end or into the region of the upper end of (a), a partial reactant stream S comprising ROH is introduced in vapour form _BE1 . This makes it possible to reduce the reaction column RR _B The size of the lower region of (a). When in particular in the reaction column RR _B Is fed in vapour form to a partial reactant stream S comprising ROH, in particular methanol _BE1 Then in the reaction tower RR _B Is employed with only a portion, in particular from 10% to 70% by weight, preferably from 30% to 50% by weight, based in each case on the total amount of the alcohol ROH employed in the optionally present step (a 2), and in the presence of M _B Reactant stream S of OH _BE2 Preferably 1 to 10 theoretical trays, particularly preferably 1 to 3 theoretical trays, are added to the remainder as a vapour in a single stream or divided into a plurality of substreams.

Then according to the reaction described above<1>In the reaction tower RR _B In a reactant stream S comprising ROH _BE1 And comprises M _B Reactant stream S of OH _BE2 Reacting to produce M _B OR and H ₂ O, wherein these products react with the reactants ROH and M as a result of equilibrium reactions involved _B A mixture of OH's is present. Thus, in the optional step (a 2) of the process according to the invention, in the reaction column RR _B To obtain crude product RP _B The crude product RP _B Not only containing the product M _B OR and water, and further contains ROH and M _B OH。

Obtain a mixture containing ROH and M _B Bottom product stream S of OR _BP And in RR _B The lower end of the tube is taken out.

Vapor stream S previously described as "comprising water and ROH _BB "in RR _B Preferably at the RR _B Is taken out.

Passing the vapor stream S comprising water and ROH _BB To step (b) of the method according to the invention. Said stream is combined with S before being supplied to step (b) of the process of the invention _AB Mixed or not, i.e. with S _AB Separately supplied to step (b) of the method according to the invention. Vapor stream S _BB Preference is given toGround and S _AB The resulting mixed vapor stream is then introduced into step (b) of the process of the present invention.

Is preferably optionally present in the reactant stream S _BE1 Such that the alcohol ROH simultaneously acts as the bottom product stream S _BP Alkali metal alkoxide M present in _B OR (ii) a solvent for OR. The reactant stream S is preferably selected _BE1 The amount of alcohol ROH in order to achieve the desired concentration of alkali metal alkoxide solution as comprising ROH and M in the bottom of the reaction column _B Bottom product stream S of OR _BP And taken out.

In a preferred embodiment of the optionally present step (a 2) of the process according to the invention, and in particular at S _BE2 Except that M _B In the case where water is contained in addition to OH, it is used as the reactant stream S in step (a 2) _BE1 Of the alcohol ROH and the total weight (mass; unit: kg) of the alcohol ROH used in step (a 2) as the reactant stream S _BE2 M of (A) _B The ratio of the total weight of OH (mass; unit: kg) is from 1 to 50, more preferably from 5 to 48, still more preferably from 9 to 35, still more preferably from 10 to 30, still more preferably from 1 to 1, most preferably from 13.

Operating the column RR with or without, preferably without, reflux _B 。

"without reflux" is understood to mean the RR _B A vapor stream S comprising water and ROH withdrawn at the upper end of (A) _BB Is completely supplied to the rectification column RD according to step (b) ₁ . A vapor stream S comprising water and ROH _BB Preferably in the form of a vapour to the rectification column RD ₁ 。

"with reflux" is understood to mean the RR of the corresponding column, i.e.in step (a 2) _B A vapor stream S comprising water and ROH withdrawn at the upper end of (A) _BB Not completely discharged, i.e. not completely supplied to first rectifying column RD in step (b) ₁ But is at least partially, preferably partially, recycled as reflux to the respective column, reaction column RR in step (a 2) _B . In the case where such reflux is established, the reflux ratio is preferably 0.05 to 0.99, more preferably 0.1To 0.9, still more preferably 0.11 to 0.34, particularly preferably 0.14 to 0.27, and very particularly preferably 0.17 to 0.24. Can be obtained by mixing a condenser K _RRB Reaction column RR attached to the respective column, step (a 2) _B At the top of the condenser K to establish a reflux _RRB Medium vapor stream S _BB At least partially condensed and returned to the corresponding column, reaction column RR in step (a 2) _B 。

In the reaction tower RR _B In the embodiment in which the reflux is established, in the optional step (a 2), as the reactant stream S _BE2 Alcohol M of _B OH may also be at least partially, preferably partially, mixed with the refluxed stream and the mixture thus obtained is supplied to step (a 2).

In particular at a temperature T of from 25 ℃ to 200 ℃, preferably from 45 ℃ to 150 ℃, more preferably from 47 ℃ to 120 ℃, more preferably from 60 ℃ to 110 ℃ _3B The optional step (a 2) of the process according to the invention is then carried out.

In particular at a pressure p of from 0.5 bar to 40 bar, preferably from 0.75 bar to 5 bar, more preferably from 1 bar to 2 bar, more preferably from 1 bar to 1.8 bar, still more preferably from 1.1 bar to 1.6 bar _3B The optional step (a 2) of the process according to the invention is then carried out. The essential feature of the invention is that when the pressure p is established _3B The method comprises the following steps: p is a radical of formula ₁ >p _3B . In particular also p _3B >p ₂ 。

In a preferred embodiment, the reaction column RR _B Comprising at least one evaporator, in particular selected from the group consisting of intermediate evaporators V _ZB And a bottom evaporator V _SB . Reaction tower RR _B Particularly preferably at least one bottom evaporator VS _3B 。

In the optional step (a 2) of the process according to the invention, in the reaction column RR _B Is withdrawn at the lower end and contains ROH and M _B Bottom product stream S of OR _BP 。

Preferably, the reaction column RR _B Comprising at least one bottom evaporator VS _3B Then the bottom product stream S _BP At least partially passing through the bottom evaporator VS _3B To at least partially remove ROH, thereby generating S _BP Compared with M having an improved mass fraction _B Bottom product stream S of OR _BP* 。

With a bottom product stream S _BP M in (1) _B Mass fraction of OR, bottom product stream S _BP* M in (1) _B The mass fraction of OR is increased in particular by at least 1%, preferably by at least 2%, more preferably by at least 5%, still more preferably by at least 10%, still more preferably by at least 20%, still more preferably by at least 30%, still more preferably by at least 40%, still more preferably by at least 50%, still more preferably by at least 100%, still more preferably by at least 150%.

Preferably, when S is used _BP When, or if, at least one bottom evaporator VS is used _3B Wherein the bottom product stream S is _BP At least partially passing through the at least one bottom evaporator VS _3B To at least partially remove ROH, based in each case on S _BP /S _BP* Total mass of (S) _BP* From 1 to 50 wt%, preferably from 5 to 32 wt%, more preferably from 10 to 32 wt%, most preferably from 15 to 30 wt% of M in ROH _B Mass fraction of OR.

Based on S _BP /S _BP* Total mass of (S) _BP /S _BP* The mass fraction of residual water in (a) is preferably<1% by weight, preferably<0.1% by weight, more preferably<0.01 wt%.

Based on S _BP /S _BP* Total mass of (S) _BP /S _BP* Reactant M in (1) _B The mass fraction of OH is preferably<1% by weight, preferably<0.1% by weight, more preferably<0.01 wt%.

In the embodiment of the process of the invention which also carries out step (a 2), it is preferred that the bottom product stream S is _AP At least partially passing through the bottom evaporator VS _3A And from S _AP At least partially removing ROH to produce a product with S _AP Compared with M with improved mass fraction _A Bottom product stream S of OR _AP* And/or, preferablyAnd, passing the bottom product stream S _BP At least partially passing through the bottom evaporator VS _3B And from S _BP At least partially removing ROH to produce a sum with S _BP M compared to an improved mass fraction _B Bottom product stream S of OR _BP* 。

In the embodiment of the invention in which step (a 2) is carried out, step (a 2) of the process according to the invention is carried out simultaneously and spatially separately from step (a 1). Through two reaction towers RR _A And RR _B Steps (a 1) and (a 2) are performed to ensure spatial separation.

In an advantageous embodiment of the invention, the reaction column RR _A And RR _B Is accommodated in a column shell, wherein the column is at least partially subdivided by at least one dividing wall (dividing wall). According to the invention, such a tower with at least one dividing wall will be referred to as "DWC". Such divided wall columns are familiar to the person skilled in the art and are described, for example, in U.S. Pat. No. 2,295,256, EP 0 122 A2, EP 0 126 288 A2, WO 2010/097318 A1 and I.

Lj.

Chemical Engineering and Processing 2010,49, 559-580. In a dividing wall column suitable for the process according to the invention, the dividing wall preferably extends to the bottom (floor) and particularly preferably spans at least one quarter, more preferably at least one third, still more preferably at least one half, still more preferably at least two thirds, still more preferably at least three quarters of the height of the column. They divide the column into at least two reaction spaces in which spatially separated reactions can take place. The reaction spaces provided by the at least one partition wall may have the same or different dimensions.

In this embodiment, the bottom product stream S _AP And S _BP Can be atAre taken out separately in the respective zones separated by the partition wall and are preferably conveyed through a bottom evaporator VS attached to each reaction space formed by at least one reaction wall _3A /VS _3B Wherein at least partially from S _AP /S _BP Removing ROH to produce S _AP* /S _BP* 。

4.3 step (b) of the method of the invention

In step (b) of the process according to the invention, a stream of vapour S is caused to flow _AB And, if step (a 2) is carried out, the vapour stream S obtained _BB Is sent to a first rectifying tower RD ₁ In (2), the vapor stream S _BB And S _AB Mixed with or with S _AB The transfer is carried out separately from the other,

to be in a rectifying tower RD ₁ To obtain a mixture G comprising water and ROH _RD1 。

In an optionally present embodiment of the process according to the invention which has been subjected to step (a 2), the vapour stream S _BB Preferably with S _AB Mixing, and then mixing the obtained mixed vapor S _ABB Is introduced into a rectification column RD ₁ In (1).

In an embodiment of the invention (when p is _3A <p ₁ /p _3B <p ₁ While) the vapor stream S is being vaporized _AB And a vapour stream S in the case where the optional step (a 2) has been carried out _BB Conveyed to a rectifying column RD ₁ Before, they may be compressed. This can be done via a compressor VD ₃₁ To be implemented. However, at p _3A >p ₁ And p is _3B >p ₁ In the embodiment of the invention, the compressor VD ₃₁ Is unnecessary, so that its supply and the electrical energy required for this purpose can be saved.

It is to be understood that even when the optional step (a 2) is carried out and S is added _BB And S _AB Are introduced into a rectification column RD respectively ₁ In the embodiment of (1), S _AB And S _BB In the rectifying column RD ₁ Thus undergoing mixing, and therefore after step (b), in a first rectification column RD ₁ Always get the package inMixture G containing water and ROH _RD1 。

Any desired rectification column known to the person skilled in the art can be used as rectification column RD in step (b) of the process according to the invention ₁ . Rectifying column RD ₁ Preferably comprising internals. Suitable internals are, for example, trays, non-structured packings or structured packings. As the tray, a bubble cap tray, a sieve plate, a float valve tray, a tunnel tray, or a slit tray is generally used. The non-regular packing is typically a bed of random packing elements. The packing elements usually used are Raschig rings, pall rings, bell saddles or

Saddle packing. Structured packings such as those available from Sulzer under the trade name

Those that are commercially available. In addition to the internals mentioned, further suitable internals are known to the person skilled in the art and can likewise be used.

Preferred internals have a low specific pressure drop per theoretical plate. The structured packing and random packing units have, for example, a significantly lower pressure drop per theoretical plate than the trays. This has the following advantages: the pressure drop in the rectification column is kept as low as possible, while the mechanical power of the compressor and the alcohol/water mixture G to be evaporated _RD1 The temperature of (a) is thus kept low.

When rectifying column RD ₁ When structured or non-structured packing is present, the packing may be divided or may be in the form of continuous packing. However, typically at least two layers of packing are provided, one at the vapour stream S _AB Feed point/two vapor streams S of _AB And S _BB Above the feed point of (A), and a layer of packing is in the vapour stream S _AB Feed point/two vapor streams S _AB And S _BB Feed point/mixed vapor S of _ABB Below the feed point of (a). If non-structured packing is usedE.g. random packing, the random packing units are typically arranged on suitable sieve plates or sieve trays (mesh tray).

At the end of step (b) of the process according to the invention, in rectification column RD ₁ Finally a mixture G comprising water and ROH is obtained _RD1 . Mixture G _RD1 Is especially composed of a vapor stream S _AB And if step (a 2) is carried out, in particular by two vapor streams S respectively _AB And S _BB Results in (c).

4.4 step (c) of the method of the invention

In step (c) of the process according to the invention, in a first rectification column RD ₁ At a pressure p ₁ And temperature T ₁ The mixture G comprising water and ROH _RD1 Separated to be in RD ₁ Of the upper end (= top) of (a) a vapour stream S comprising ROH _RDB1 And in RD ₁ A bottom stream S comprising water and ROH at the lower end (= bottom) of (a) _RDS1 。

Except for condition p ₁ >p ₂ Beyond, RD ₁ Pressure p in ₁ The selection can be made by those skilled in the art based on their knowledge in the art. Said pressure p ₁ Preferably 1 to 20 bar, preferably 1 to 15 bar, more preferably 2 to 14 bar, still more preferably 4.00 to 11.00 bar, still more preferably 6.00 to 10.00 bar, still more preferably 7.00 to 8.90 bar, wherein at the same time p ₁ >p ₂ 。

RD ₁ Temperature T in ₁ The selection can be made by those skilled in the art based on their knowledge in the art. Said temperature T ₁ Preferably from 40 ℃ to 220 ℃, preferably from 60 ℃ to 190 ℃.

In a preferred embodiment, p is _3A >p ₂ And further in the case where step (a 2) is carried out, p _3B >p ₂ . Due to this established pressure, with p _3A <p ₂ /p _3B <p ₂ Surprisingly, the overall energy requirements of the process are minimized.

The separation according to step (c) of the process of the invention is an alcohol/water mixture G as known to the person skilled in the art _RD1 The distillation separation of (3).

In the rectifying column RD ₁ To obtain a bottom stream S still comprising alcohol ROH _RDS1 . Based on S _RDS1 Total mass of (S) _RDS1 Contains ROH in a mass fraction of in particular from 0.005 to 95% by weight, preferably from 25 to 95% by weight. Apart from the alcohol ROH, S _RDS1 Preferably also substantially comprising water.

In a preferred embodiment of the present invention, S _RDB1 At least partially used as the reactive distillation column RR _A Of (2) a reactant stream S _AE1 And, if step (a 2) is carried out, can be used alternatively or additionally as the reactive distillation column RR _B Of (2) _BE1 。

In addition, in the rectification column RD ₁ Also obtains a vapor stream S comprising ROH _RDB1 . In each case based on S _RDB1 Of the total mass of the vapor stream S _RDB1 The preferred mass fraction of ROH in (b) is ≥ 99 wt%, preferably ≥ 99.6 wt%, more preferably ≥ 99.9 wt%, with the remainder being in particular water.

In step (c), the vapor S obtained in step (a 1) or in steps (a 1) and (a 2) is subjected to _AB Or S _AB And S _BB Subjected to distillation separation. These vapors contain essentially alcohol ROH and water. In particular, S _AB Or S _AB And S _BB Each being a water/alcohol mixture, wherein the mass fraction of ROH is preferably>80% by weight, more preferably>85% by weight, even more preferably>90% by weight (based on S) _AB Or S _AB And S _BB Total mass of). Thus, in particular, G _RD1 Also an alcohol/water mixture, wherein the mass fraction of ROH is preferably>80% by weight, more preferably>95% by weight, still more preferably>90% by weight (based on G) _RD1 Total mass of).

4.5 step (d) of the method of the present invention

In accordance with the present inventionIn step (d) of the inventive process, the bottom stream S is passed _RDS1 Wholly or partly, preferably partly, to the second rectification column RD ₂ In (1).

This is carried out in a second rectification column RD ₂ In which a mixture G comprising water and ROH is produced _RD2 。

In the process of S _RDS1 Is partially transmitted to RD ₂ In an embodiment of the present invention, the scheme is particularly performed so that the first rectifying column RD is passed through ₁ The bottom stream S discharged _RDS1 First part S of _RDS11 Is sent to a second rectifying tower RD ₂ And from the first rectification column RD ₁ The bottom stream S discharged _RDS1 Second part S of _RDS12 Recycled to the first rectifying column RD ₁ In (1). Even more preferably, energy is transferred to S _RDS12 It is still more preferable to heat S _RDS12 . After S has been reduced _RDS12 Recycled to RD ₁ In the case of RD, it is in ₁ Neutral with G _RD1 Undergoes mixing and thus provides a process for separating G according to step (c) _RD1 The energy of (c).

In this preferred embodiment of step (d) of the process according to the invention, it is even more preferred that S _RDS11 And S _RDS12 The ratio of mass (in kg) of 9.

In this preferred embodiment of step (d) of the process according to the invention, it is possible to pass on stream S _RDS12 Energy is supplied. In a preferred embodiment, this is accomplished by passing stream S _RDS12 Passing through the bottom evaporator VS _RD1 Is achieved in that energy is transferred from the heat transfer medium to S _RDS12 . When S is _RDS12 And the heat transfer medium passing through the bottom evaporator VS _RD1 Such energy transfer can advantageously be carried out. At S _RDS12 Recycled to the reaction tower RR _A After neutralization, then S _RDS12 Transferring energy to G _RD1 。

Any desired rectification column known to the person skilled in the art can be used as the rectification in step (d) of the process according to the inventionDistillation column RD ₂ . Rectifying column RD ₂ Preferably containing internals. Suitable internals are, for example, trays, non-structured packings or structured packings. As the tray, a bubble cap tray, a sieve plate, a float valve tray, a tunnel tray, or a slit tray is generally used. The non-regular packing is typically a bed of random packing elements. The packing elements usually used are Raschig rings, pall rings, bell saddles or

Saddle packing. Structured packings are, for example, from Sulzer under the trade name

Those commercially available. In addition to the internals mentioned, further suitable internals are known to the person skilled in the art and can likewise be used.

Preferred internals have a low specific pressure drop per theoretical plate. The structured packing and random packing units have, for example, a significantly lower pressure drop per theoretical plate than the trays. This has the following advantages: rectifying column RD ₂ The pressure drop in the condenser is kept as low as possible, and the mechanical power of the compressor and the alcohol/water mixture G to be evaporated _RD2 The temperature of (a) is kept low.

When rectifying column RD ₂ When structured or non-structured packing is present, the packing may be divided or may be in the form of continuous packing. However, typically at least two layers of packing are provided, one at the flow S _RDS1 Part S _RDS1 In particular S _RDS12 And a layer of packing is below the relevant feed point. If non-structured packing is used, such as random packing, the random packing elements are typically arranged on suitable sieve plates or sieve trays.

To RD ₂ Middle S _RDS1 Part S _RDS1 Preferably is S _RDS12 At least partially liquid.

It is therefore further preferred to feed them into RD via a liquid compressor or pump P ₂ In (1).

At the end of step (d) of the process according to the invention, in rectification column RD ₂ Finally a mixture G comprising water and ROH is obtained _RD2 . Mixture G _RD2 Is particularly transmitted to the RD ₂ Stream S in (1) _RDS1 Partial stream S _RDS1 Preferably S _RDS12 The composition of (a) results.

4.6 step (e) of the method of the present invention

In step (e) of the process according to the invention, at a pressure p ₂ And temperature T ₂ The mixture G comprising water and ROH _RD2 Separated to be in RD ₂ Comprises a vapor stream S of ROH _RDB2 And in RD ₂ A bottom stream S comprising water and optionally ROH of (a) _RDS2 。

Except for condition p ₁ >p ₂ Beyond, RD ₂ Pressure p of ₂ The selection can be made by those skilled in the art based on their knowledge in the art. Said pressure p ₂ Preferably 1 to 20 bar, preferably 1 to 15 bar, more preferably 1 to 10 bar, still more preferably 1.00 to 2.00 bar, still more preferably 1.10 to 1.80 bar, still more preferably 1.10 to 1.50 bar, wherein p is at the same time ₁ >p ₂ 。

RD ₂ Temperature T in ₂ The selection can be made by those skilled in the art based on their knowledge in the art. Said temperature T ₂ Preferably from 40 ℃ to 220 ℃, preferably from 60 ℃ to 190 ℃.

The separation according to step (e) of the process of the invention is an alcohol/water mixture G as known to the person skilled in the art _RD2 The distillation separation of (3).

In the rectifying column RD ₂ Obtain a stream S _RDS2 Said stream S _RDS2 Based on S _RDS2 May comprise<1% by weight of an alcohol.

In the rectifying column RD ₂ Also obtains a vapor stream S comprising ROH _RDB2 . At each timeIn one case based on S _RDB2 Of the total mass of the vapor stream S _RDB2 The preferred mass fraction of ROH in (b) is ≥ 99 wt%, preferably ≥ 99.6 wt%, more preferably ≥ 99.9 wt%, with the remainder being in particular water.

In a preferred embodiment of the invention, S _RDB2 At least partially used as the reactive distillation column RR _A Of (2) a reactant stream S _AE1 And, if step (a 2) is carried out, can be used alternatively or additionally as the reactive rectification column RR _B Of (2) _BE1 。

In step (e), it is completely or partially transferred to second distillation column RD in step (d) ₂ Stream S in (1) _RDS1 Preferably S _RDS12 Part was subjected to distillation separation.

4.7 pressure management as a characterizing feature

The process according to the invention is characterized in that it is carried out in a rectification column RD ₁ (step (c)) and RD ₂ During operation of (step (e)), a pressure ratio is established.

Thus, p ₁ >p ₂ ，p ₁ >p _3A And in the case of performing step (a 2), p ₁ >p _3B 。

It has surprisingly been found that maintaining these pressures allows minimizing the need for energy supplied in the form of heating steam and satisfying most of the energy required for the process by electricity.

It is furthermore also more advantageous to establish the pressure such that p _3A >p ₂ And, in the case where step (a 2) is carried out, p is additionally added _3B >p ₂ . And p _3A <p ₂ /p _3B <p ₂ In contrast to the situation in which the pressure p is established in this way _3A And p _3B Reducing the total required energy requirement.

_RDB2 _RD1 4.8 characterization step (f): energy transfer from S to G

According to step (f) of the process of the inventionCharacterised in that, in addition to the pressure conditions, the energy is from S _RDB1 Is transferred to a second rectifying tower RD ₂ Mixture G of (1) _RD2 . According to the invention, "energy transfer" is to be understood in particular as meaning "heat transfer".

This step (f) and the pressure conditions according to the invention allow a particularly advantageous integration of the energy that would otherwise be dissipated, which makes it possible to satisfy a particularly large proportion of the energy requirements of the process by means of electricity instead of heating the steam. This makes the process according to the invention particularly energy efficient.

According to the present invention, the slave S can be realized in various ways familiar to those skilled in the art _RDB1 To RD ₂ G in (1) _RD2 And preferably comprises the use of S _RDB1 Heating RD ₂ G in (1) _RD2 For example via the heat transfer medium WT.

According to the invention, in step (f), the energy is in particular directly or indirectly, preferably directly, from S _RDB1 To RD ₂ G in (1) _RD2 。

4.8.1 Slave S _RDB1 To RD ₂ Middle G _RD2 Direct energy transfer of

According to the invention, the slave S _RDB1 To RD ₂ Middle G _RD2 By direct energy transfer "is understood to mean that RD is achieved ₂ Middle G _RD2 And S _RDB1 Preferably heating, so that at G _RD2 Not in contact with S _RDB1 In the case of undergoing mixing, G _RD2 And S _RDB1 Contact, thus transferring energy from S _RDB1 Is transmitted to G _RD2 . However, according to the invention, the case of direct energy transfer is to be understood as also including the following cases: at S _RDB1 Is different from S _X In the case of experiencing mixing, slave RD is realized ₂ Discharged stream S _X And S _RDB1 Preferably heating, thereby transferring energy from S _RDB1 Is transmitted to S _X And then S is _X Transmitted back to RD ₂ In the RD ₂ Middle S _X And RD ₂ G in (1) _RD2 Undergo mixing and will thereforeFrom S _RDB1 The absorbed energy is transferred to the RD ₂ G in (1) _RD2 。

In a particular embodiment of the invention, S _X Is selected from S _RDS22 、S _RDX2 。

The mixing-free contacting is achieved by methods known to the person skilled in the art, for example by contacting via a separating wall made of metal, plastic or the like, in particular in the heat exchanger WT, preferably the condenser K or an evaporator V, which is selected in particular from the bottom evaporator VS and the intermediate evaporator VZ.

According to the present invention, it is preferred that the removal of S from S is carried out according to at least one of the steps (α -i), (α -ii), (α -iii), more preferably according to at least one of the steps (α -i), (α -ii) _RDB1 To the second rectifying column RD ₂ Mixture G of (1) _RD2 Direct energy transfer.

(α -i) transfer energy from S _RDB1 To slave RD ₂ The bottom stream S discharged _RDS2 S of _RDS22 And then S is _RDS22 Recycled to RD ₂ In (1). This step (. Alpha. -i) also includes embodiments wherein: energy is initially from S _RDB1 Preferably to the total bottom stream S via a heat exchanger WT _RDS2 Then only S _RDS22 Partially flowing S from the bottom _RDS2 Separating, and then separating S _RDS22 Recycled to RD ₂ In (1).

(α -ii) will react with S _RDB2 And S comprising ROH and water _RDS2 Different at least one stream S _RDX2 From RD ₂ Discharging and then transferring energy from S _RDB1 Is transmitted to S _RDX2 Preferably via heat exchanger WT, and is passed S _RDX2 Recycled to RD ₂ In (1).

Preferably, in RD ₂ Said vapor stream S of _RDB2 Take out S from below _RDX2 . Then S _RDX2 In particular from the bottom stream S _RDX2S Intermediate stream S _RDX2Z 。

Bottom stream S _RDX2S Is a stream that is at RD ₂ Is at the discharge point of S _RDS2 Discharge ofHeight of point equal or S _RDS2 Below the discharge point. Then, S may be added _RDX2S Passes through a heat exchanger WT, in particular a bottom evaporator VS, and can transfer the energy therein from S _RDB1 Is transmitted to S _RDX2S 。

Intermediate stream S _RDX2Z Is a stream which is at RD ₂ At the upper discharge point of S _RDB2 And S _RDS2 Between the discharge points. Then S may be _RDX2Z From RD ₂ Is discharged and conveyed through a heat exchanger WT, in particular an intermediate evaporator VZ, and can transfer energy from S _RDB1 S transmitted to it _RDX2Z 。

(α -iii) reacting S _RDB1 Transmitted through RD ₂ Thus transferring energy from S _RDB1 Is transmitted to G _RD2 Preferably via heat exchanger WT. For example when S is to be passed through a catheter _RDB1 Conveyed through a rectification column RD ₂ Through the surface of said conduit, S _RDB1 Transfer energy to RD ₂ G in (1) _RD2 Such an embodiment may be implemented.

4.8.2 Slave S _RDB1 To RD ₂ G in (1) _RD2 Indirect energy transfer of

According to the invention, the slave S _RDB1 To RD ₂ G in (1) _RD2 By indirect energy transfer "is understood to mean in RD ₂ In implementation of G _RD2 And S _RDB1 Preferably heating, so that G _RD2 Not in contact with S _RDB1 By direct contact, but with G _RD2 And S _RDB1 Different at least one additional, preferably exactly one additional heat transfer medium W ₁ At the slave S _RDB1 To RD ₂ G in (1) _RD2 During the energy transfer of (2), the heat transfer medium W ₁ Is not in contact with S _RDB1 Undergo mixing with RD ₂ G in (1) _RD2 And (4) mixing. At S _RDB1 With said at least one heat exchange medium (heat exchanger) W ₁ Without undergoing mixing, energy is transferred from S _RDB1 Is transferred to the at least one heat exchange medium W ₁ Then in the at least one heat exchange medium W ₁ And G _RD2 Without undergoing mixing, energy is transferred from the at least one heat transfer medium W ₁ To RD ₂ G in (1) _RD2 。

According to the invention, indirect energy transfer is to be understood as also including the case: at S _RDB1 With said at least one heat exchange medium W ₁ Without undergoing mixing, energy is transferred from S _RDB1 To the at least one, preferably exactly one, heat transfer medium W ₁ And then in the at least one heat transfer medium W ₁ And S _X Without undergoing blending, slave RD is realized ₂ Discharged stream S _X With said at least one heat transfer medium W ₁ Is preferably heated, thereby transferring energy from the at least one heat transfer medium W ₁ Is transmitted to S _X Then, S is _X Recycled to RD ₂ Wherein said S _X And RD ₂ G in (1) _RD2 Undergoes mixing, thus S _RDB1 The absorbed energy is transferred via the at least one heat transfer medium W ₁ To RD ₂ G in (1) _RD2 。

"at least one heat transfer medium W ₁ "includes the following cases: firstly, W is ₁ To and G _RD2 And S _RDB1 Different one or more additional heat transfer media W ₂ 、W ₃ 、W ₄ 、W ₅ Etc., and the last of these heat transfer media, is referred to as "W _Y ", and RD ₁ G in (1) _RD2 Contact, thereby transferring energy, preferably heat, from W _Y Is transmitted to G _RD2 But W _Y And G _RD2 Without undergoing mixing. At W _Y And S _X Without undergoing mixing, the energy, preferably thermal energy, may likewise be derived from W _Y To slave RD ₂ Discharged stream S _X And then S is _X Recycled to RD ₂ In which S is _X And RD ₂ G in (1) _RD2 Undergoes mixing, thereby mixing W _Y The absorbed energy is transferred to the RD ₂ G in (1) _RD2 。

The contacting is preferably carried out in each case in a heat exchanger WT, preferably a condenser K or an evaporator V, which is selected in particular from the bottom evaporator VS and the intermediate evaporator VZ.

According to the present invention, it is preferred that the removal of S from S is carried out according to at least one of steps (β -i), (β -ii), (β -iii), more preferably according to at least one of steps (β -i), (β -ii) _RDB1 To the second rectifying column RD ₂ Mixture G of (1) _RD2 Indirect energy transfer of (2).

(β -i) will be driven from RD ₂ The bottom stream S discharged _RDS2 S of _RDS22 Is partially recycled to the second rectification column RD ₂ In (1). To transfer energy from S _RDB1 To at least one of S and S _RDS22 Different heat transfer media W _i1 And then from the at least one heat transfer medium W _i1 Is transmitted to S _RDS22 And then S is _RDS22 Recycled to RD ₂ Performing the following steps;

this step (. Beta. -i) also includes embodiments wherein: energy is initially derived from said at least one, preferably exactly one and S _RDS22 Different heat transfer media W _i1 Is transferred to the total bottom stream S, preferably via a heat exchanger WT _RDS2 Then only S _RDS22 Partially flowing S from the bottom _RDS2 Separating out S _RDS22 Recycled to RD ₂ In (1).

(beta-ii) reacting at least one with S _RDB2 And S comprising ROH and water _RDS2 Different flows S _RDX2 From RD ₂ And (4) discharging. To transfer energy from S _RDB1 To at least one, preferably exactly one and S _RDX2 Different heat transfer media W _ii1 Preferably via a heat exchanger WT and then from the at least one heat transfer medium W _ii1 Is transmitted to S _RDX2 And then S is _RDX2 Recycled to RD ₂ In (1).

Preferably, in RD ₂ Said vapor stream S of _RDX2 Taken out of the bottom of S _RDB2 . Then S _RDX2 In particular from the bottom stream S _RDX2S Intermediate stream S _RDX2Z 。

Bottom stream S _RDX2S Is the stream that is at RD ₂ At the upper discharge point of S _RDS2 Of the same height or S as the discharge point _RDS2 Below the discharge point. Then, S may be added _RDX2S Passes through a heat exchanger WT, in particular a bottom evaporator VS, and the energy therein is taken from S _RDB1 Is transmitted to S _RDX2S 。

Intermediate stream S _RDX2Z Is the stream that is at RD ₂ Upper discharge point is at S _RDB2 And S _RDS2 Between the discharge points. Then, S may be added _RDX2Z From RD ₂ Is discharged and conveyed through a heat exchanger WT, in particular an intermediate evaporator VZ, and in which energy is taken from S _RDB1 Is transmitted to S _RDX2Z 。

(beta-iii) conversion of energy from S _RDB1 To at least one and G _RD2 Different heat transfer media W _iii1 And then the at least one heat transfer medium W is _iii1 Transmitted through RD ₂ Thus transferring energy from the at least one heat transfer medium W _iii1 Is transmitted to G _RD2 。

For example when the at least one heat transfer medium W is fed via a conduit _iii1 Conveyed through a rectification column RD ₂ Said conduit surface transferring energy from said at least one heat transfer medium W _iii1 To RD ₂ G in (1) _RD2 Such an embodiment may be implemented.

Usable heat transfer medium W ₁ 、W ₂ 、W ₃ 、W ₄ 、W ₅ At least one heat exchange medium W _i1 At least one heat exchange medium W _ii1 At least one heat exchange medium W _iii1 Any heat transfer medium known to those skilled in the art is included. Such heat transfer medium is preferably selected from water; an alcohol-water solution; salt-water solutions, also including for example ionic liquids, such as LiBr solutions, dialkyl imidazolium salts, such as in particular dialkyl imidazolium dialkyl phosphates; mineral oils, such as diesel; heat transfer oils, such as silicone oils; bio-oils, such as limonene; aromatic hydrocarbons, e.g. bisAnd (3) benzoyl toluene. The most preferred heat transfer medium is water.

Useful salt-water solutions are also described, for example, in DE 10 2005 028 451 A1 and WO 2006/134015 A1.

4.9 addition of fresh alcohol

The alcohol ROH is consumed in the process according to the invention and therefore needs to be replaced by fresh alcohol ROH, in particular in the continuous process mode.

Fresh alcohol is added in particular to a column selected from the rectification column RD ₁ And a rectifying tower RD ₂ And a reaction rectifying tower RR _A And if step (a 2) is carried out, alternatively or additionally to the reactive rectification column RR _B In (1).

Thus, in a preferred embodiment of the invention, S will be reacted with an ROH comprising compound _AE1 And S _BE1 Different flows S _XE1 Is added into a rectifying tower RD ₁ And a rectifying column RD ₂ And a reaction rectifying tower RR _A And if step (a 2) is carried out, may alternatively or additionally be added to the reactive distillation column RR _B In (1).

In particular, the direct use of fresh alcohol ROH as ROH-containing reactant stream S _AE1 Is introduced into a reaction tower RR _A Or in the embodiment in which step (a 2) is carried out, to the reaction column RR _A And RR _B In (1).

In the process according to the invention, it is further preferred that the vapour stream S comprising ROH is passed to a reactor _RDB1 At least partly as a reactant stream S in step (a 1) _AE1 And optionally as a reactant stream S in step (a 2) _BE1 . Steam flow S _RDB2 May alternatively or additionally be used at least partly as reactant stream S in step (a 1) _AE1 And optionally as a reactant stream S in step (a 2) _BE1 。

In the process of S _RDB1 And S _RDB2 At least partly as a reactant stream S in step (a 1) _AE1 And optionally as a reactant stream S in step (a 2) _BE1 In a particularly preferred embodiment, canWill S _RDB1 And S _RDB2 Are supplied separately from each other to the respective reactive distillation column RR _A /RR _B Or first mixed with each other and then supplied to the respective reactive distillation columns RR _A /RR _B 。S _RDB1 And S _RDB2 Preferably first mixed with each other and then supplied to the respective reactive distillation column RR _A /RR _B 。

In this preferred embodiment, it is still more preferred that the fresh alcohol ROH is fed to the rectification column RD ₁ And RD ₂ Of (b), preferably RD ₁ 。

When adding fresh alcohol ROH into the rectifying tower RD ₁ Or RD ₂ Preferably, the fresh alcohol is supplied in the reinforcement section of the respective rectification column or directly at the top of the respective rectification column. The optimum feed point depends on the water content of the fresh alcohol employed and also on the vapour stream S _RDB1 /S _RDB2 Desired residual water content of (a). The higher the proportion of water in the alcohol employed and the higher the vapour stream S _RDB1 /S _RDB2 The higher the purity requirement, in the rectification column RD ₁ /RD ₂ The more advantageous is the feed opening at several theoretical trays below the top of (a). In the rectifying column RD ₁ /RD ₂ Is preferably no more than 20 theoretical trays, especially 1 to 5 theoretical trays, below the top of the tray.

When adding fresh alcohol ROH into the rectifying tower RD ₁ /RD ₂ At a temperature not higher than the boiling point, preferably at room temperature, in the rectification column RD ₁ /RD ₂ The fresh alcohol is added at the top. The fresh alcohol may have a dedicated feed inlet provided for it, or in the rectification column RD ₁ /RD ₂ May be mixed with the part of the alcohol after condensation and supplied together to the rectification column RD ₁ /RD ₂ . In this case, it is particularly preferred to feed fresh alcohol into the condensate vessel, in which the vaporous stream S is collected _RDB1 /S _RDB2 Condensed alcohol.

5. Examples of the embodiments

5.1 example 1 (Hair StichesMing)

The arrangement according to example 1 corresponds to a double tower interconnection according to FIG. 1, wherein p ₁ >p _3A >p ₂ 。

At 25 ℃ a stream S of 5t/h aqueous NaOH (50% by weight) _AE2 <3A02>Is supplied to the reaction column RR _A <3A>Of the bottom plate. In the reaction tower RR _A <3A>Is supplied with a stream S of 70.2t/h of vaporous methanol in countercurrent over the bottom _AE1 <3A01>. At a pressure p of 1.6 bar _3A Lower operation of the reaction column RR _A <3A>. In the tower RR _A <3A>At the bottom of (2) is withdrawn 10.8t/h of a product stream S which is virtually free of water _AP* <3A08>(30% by weight sodium methoxide in methanol). In the reaction tower RR _A <3A>Evaporator VS _3A <3A06>Here, the use of heating steam introduces about 0.7MW of heating power. In the reaction tower RR _A <3A>Is withdrawn as a vaporous methanol-water stream S _AB <3A03>. Part of this stream is passed through a condenser K _RRA <3A05>Recycled to the reaction tower RR _A <3A>And in the compressor VD ₃₁ <10>The remaining part (64.4 t/h) is compressed to 7.1 bar and supplied to the first rectification column RD ₁ <1>Wherein about 4MW of compressor power is necessary. At p is ₁ Operation of the rectification column RD at = -7 bar ₁ <1>. In the rectifying column RD ₁ <1>Is supplied with a liquid fresh methanol stream (not shown in fig. 1) of 9.5t/h and a vapor methanol stream S is withdrawn _RDB1 <101>. Via a condenser K _RD1 <102>Will S _RDB1 <101>Is recycled to the column RD ₁ <1>In (1). Will S _RDB1 <101>The remaining part (42.9 t/h) of the reaction is supplied to the reaction column RR _A <3A>. Tower RD ₁ <1>Condenser K of _RD1 <102>While being a second rectification column RD ₂ <2>Evaporator VS _RD2 Is a tower RD ₂ <2>Heating power is provided. The embodiment according to example 1 utilizes direct contact, with condenser K _RD1 <102>Simultaneously as a bottom evaporator VS _RD2 <204>。

In the rectifying column RD ₁ <1>Is discharged with a liquid stream S of a water-methanol mixture _RDS1 <103>Said stream S _RDS1 <103>30.9t/h S in (1) _RDS12 <104>Part of it is sent to a rectification column RD ₂ <2>And flow S _RDS1 <103>The remainder of (1) is regarded as S _RDS11 <105>Recycled to RD ₁ <1>In (1). In the rectifying column RD ₁ <1>Evaporator VS _RD1 <106>Here, a heating power of about 5.4 MW is introduced via the heating steam.

At a pressure p of 1.1 bar ₂ Lower operation of the rectification column RD ₂ <2>. In the rectifying column RD ₂ <2>Taking off a stream S of vaporous methanol at the top _RDB2 <201>. Via a condenser K _RD2 <203>Will S _RDB2 <201>Is recycled in part to column RD ₂ <2>In (1). Will S _RDB2 <201>The remaining part (27.3 t/h) of (A) is supplied to the reaction column RR _A <3A>. In a compressor VD ₂₃ <13>In which the vapor stream S is evaporated _RDB2 <201>Is compressed to 2 bar, wherein a compressor power of about 0.6MW is necessary. In the rectifying column RD ₂ <2>Is discharged with a liquid stream S of 3.7t/h of water _RDS2 <202>(contaminated with 500ppmw of methanol). For rectifying column RD ₂ <2>Evaporation (bottom evaporator VS shown in fig. 1 due to the direct heat integration achieved) _RD2 <204>Is made of a condenser K _RD1 <102>Co-undertake) via a tower RD ₁ <1>The heat integration of (2) introduces about 14.8MW of heating power to S _RDS2 <202>S of _RDS22 <222>And (4) partial.

Will be at RD ₁ <1>And RD ₂ <2>Is withdrawn as a stream S of vaporous methanol at the top _RDB1 <101>And S _RDB2 <201>Is mixed with the corresponding, non-recirculated portion and recirculated to the reaction column RR _A <3A>The bottom of (a).

In this embodiment, a total of about 6.1MW of heating power via heating steam and about 4.6MW of electrical power (compressor power) are required and must be provided externally.

5.2 example 2 (inventive)

The arrangement according to example 2 corresponds to the double tower interconnection according to fig. 2, wherein p ₁ >p ₂ >p _3A 。

At 25 ℃ a stream S of 5t/h aqueous NaOH solution (50% by weight) _AE2 <3A02>Is supplied to the reaction column RR _A <3A>Of the bottom plate. In the reaction tower RR _A <3A>Is supplied with a stream S of 70.2t/h of vaporous methanol in countercurrent over the bottom _AE1 <3A01>. At a pressure p of 1.1 bar _3A Lower operation of the reaction column RR _A <3A>. In the tower RR _A <3A>At the bottom of which a product stream S of 10.8t/h is taken off which is virtually free of water _AP* <3A08>(30% by weight sodium methoxide in methanol). In the reaction tower RR _A <3A>Evaporator VS _3A <3A06>Here, the use of heating steam introduces about 2.4MW of heating power. In the reaction tower RR _A <3A>Is withdrawn as a vaporous methanol-water stream S at the top _AB <3A03>. Part of this stream is passed through a condenser K _RRA <3A05>Recycled to the reaction tower RR _A <3A>And in the compressor VD ₃₁ <10>The remaining part (64.4 t/h) is compressed to 9 bar and supplied to the first rectification column RD ₁ <1>Wherein a compressor power of about 5.8MW is necessary. At p ₁ (ii) operating the column RD at = -8.9 bar ₁ <1>. In the rectifying column RD ₁ <1>Is supplied with a liquid fresh methanol stream (not shown in fig. 2) of 9.5t/h and a vapour methanol stream S is withdrawn _RDB1 <101>. Via a condenser K _RD1 <102>Will S _RDB1 <101>Is recycled to the column RD ₁ <1>In (1). Will S _RDB1 <101>The remaining part (42.9 t/h) of the reaction is supplied to the reaction column RR _A <3A>. Tower RD ₁ <1>Condenser K of _RD1 <102>While being the second rectifying column RD ₂ <2>Evaporator VS _RD2 <204>Is a tower RD ₂ <2>Providing heating power. The embodiment according to example 2 utilizes direct contact, wherein the condenser K _RD1 <102>Simultaneously as a bottom evaporator VS _RD2 <204>。

In the rectifying column RD ₁ <1>At the bottom of which a liquid stream S of a water-methanol mixture is discharged _RDS1 <103>Said stream S _RDS1 <103>31.9t/h S in (1) _RDS12 <104>Part of it is sent to a rectification column RD ₂ <2>And flow S _RDS1 <103>As the remainder of S _RDS11 <105>Recycled to RD ₁ <1>In (1). In the rectifying column RD ₁ <1>Evaporator VS _RD1 <106>Here, about 5.2 MW of heating power is introduced via the heating steam.

At a pressure p of 1.5 bar ₂ Lower operation of the rectification column RD ₂ <2>. In the rectifying column RD ₂ <2>At the top of which a stream S of vaporous methanol is withdrawn _RDB2 <201>. Via a condenser K _RD2 <203>Will S _RDB2 <201>Is recycled to the column RD ₂ <2>In (1). Will S _RDB2 <201>The remaining part (28.2 t/h) of (A) is supplied to the reaction column RR _A <3A>. In the rectifying column RD ₂ <2>Is discharged with a liquid stream S of 3.7t/h of water _RDS2 <202>(contaminated with 500ppmw of methanol). For rectifying column RD ₂ <2>Evaporation of (due to direct heat integration, bottom evaporator VS shown in fig. 1) _RD2 <204>Is formed by a condenser K _RD1 <102>Co-undertake) via a tower RD ₁ <1>The heat integration of (2) introduces about 15.9MW of heating power to S _RDS2 <202>S of _RDS22 <222>And (4) partial.

In this embodiment, a total of about 7.6MW of heating power via heating steam and about 5.8MW of electric power (compressor power) are required and must be provided externally.

5.3 example 3 (not according to the invention)

The arrangement according to embodiment 3 corresponds to the double tower interconnection according to fig. 3, wherein p ₂ >p ₁ >p _3A . In the arrangement according to embodiment 3, the intermediate evaporator VZ is likewise omitted _RD1 <107>And a tapping point as shown in figure 3<111>Is treated with the withdrawn stream S _RDX1 <112>. Condenser K _RD2 <203>At the same time is the bottom evaporator VS _RD1 <106>. Fresh methanol stream S _XE1 <205>Supplied to the rectifying column RD in FIG. 3 ₂ <2>But is supplied to RD in the setup according to embodiment 3 ₁ <1>。

At 25 ℃ a stream S of 5t/h aqueous NaOH (50% by weight) _AE2 <3A02>Is supplied to the reaction column RR _A <3A>Of the bottom plate. In the reaction tower RR _A <3A>Is supplied with a stream S of 70.2t/h of vaporous methanol in countercurrent over the bottom _AE1 <3A01>. At a pressure p of 1.1 bar _3A Bottom operation reaction column RR _A <3A>. In the tower RR _A <3A>Is withdrawn at the bottom of 10.8t/h of a product stream S which is virtually free of water _AP* <3A08>(30% by weight sodium methoxide in methanol). In the reaction tower RR _A <3A>Evaporator VS _3A <3A06>Here, the use of heating steam introduces about 1.4MW of heating power. In the reaction tower RR _A <3A>Is withdrawn overhead from the vapor of the methanol-water stream S _AB <3A03>. Via a condenser K _RRA <3A05>Recycling a portion of this stream to the reaction column RR _A <3A>And in the compressor VD ₃₁ <10>The remaining part (64.4 t/h) is compressed to 1.7 bar and supplied to the first rectification column RD ₁ <1>Wherein about 1.1MW of compressor power is necessary. At p is ₁ (ii) operating the column RD at = -1.5 bar ₁ <1>. In the rectifying column RD ₁ <1>Is supplied with a liquid fresh methanol stream S of 9.5t/h _XE1 <205>(rectification column RD in FIG. 3) ₂ <2>Shown at the top) and a vapor methanol stream S is withdrawn _RDB1 <101>. Via a condenser K _RD1 <102>Will S _RDB1 <101>Is recycled to the column RD ₁ <1>In (1). Will S _RDB1 <101>The remaining part (56.8 t/h) of the reaction is supplied to the reaction column RR _A <3A>. The embodiment according to example 3 utilizes direct contact, wherein the condenser K _RD2 <203>Acting simultaneously as a bottom evaporator VS _RD1 <106>。

In the rectifying column RD ₁ <1>Is discharged with a liquid stream S of a water-methanol mixture _RDS1 <103>Said stream S _RDS1 <103>S of 17t/h in (1) _RDS12 <104>Part of it is sent to a rectification column RD ₂ <2>And will flow S _RDS1 <103>The remainder of (1) is regarded as S _RDS11 <105>Recycled to RD ₁ <1>In (1).

Discharged stream S _RDS12 <104>At the pump P<15>To 9 bar and the stream S is added _RDS12 <104>Is supplied to the second rectifying column RD ₂ <2>. At a pressure p of 8.9 bar ₂ Lower operation of the rectification column RD ₂ <2>. In tower RD ₂ <2>Condenser K of _RD2 <203>I.e. both towers RD ₁ <1>In the evaporator of (1), is a column RD ₁ <1>About 8.2MW of heating power is provided. In the rectifying column RD ₂ <2>Is withdrawing a vaporous methanol stream S overhead _RDB2 <201>. Via a condenser K _RD2 <203>Will S _RDB2 <201>Is recycled to the column RD ₂ <2>In (1). Will S _RDB2 <201>The remaining part (13.4 t/h) of (A) is supplied to the reaction column RR _A <3A>. In the rectifying column RD ₂ <2>The bottom of which discharges a liquid stream of 3.7t/h water (contaminated with 500ppmw of methanol). In the rectifying column RD ₂ <2>Evaporator VS _RD2 <204>Here, the use of heating steam introduces about 12.9MW of heating power.

Will be at RD ₁ <1>And RD ₂ <2>Is withdrawn from the topMethanol stream S _RDB1 <101>And S _RDB2 <201>The corresponding, non-recirculated portion of the reaction mixture is mixed, depressurized and recirculated to the reaction column RR _A <3A>The bottom of (a).

In this embodiment, a total of about 14.3MW of heating power via heating steam and about 1.1MW of electric power (compressor power) are required and must be provided externally.

5.4 example 4 (not according to the invention)

The arrangement according to embodiment 4 corresponds to the double tower interconnection according to fig. 4, wherein p ₂ >p _3A >p ₁ . In the arrangement according to example 4, the intermediate evaporator VZ is likewise omitted _RD1 <107>And a discharge point shown in FIG. 4<111>Is treated with the withdrawn stream S _RDX1 <112>. Condenser K _RD2 <203>At the same time is the bottom evaporator VS _RD1 <106>. Fresh methanol stream S _XE1 <205>Supplied to rectifying column RD in FIG. 4 ₂ <2>But supplied to RD in the setup according to embodiment 4 ₁ <1>。

At 25 ℃ a stream S of 5t/h aqueous NaOH solution (50% by weight) _AE2 <3A02>Is supplied to the reaction column RR _A <3A>Of the bottom plate. In the reaction tower RR _A <3A>Is supplied with a stream S of 70.2t/h of vaporous methanol in countercurrent over the bottom _AE1 <3A01>. At a pressure p of 1.6 bar _3A Lower operation of the reaction column RR _A <3A>. In the tower RR _A <3A>10.8t/h of a product stream S containing almost no water is taken off _AP* <3A08>(30% by weight sodium methoxide in methanol). In the reaction tower RR _A <3A>Evaporator VS _3A <3A06>Here, the use of heating steam introduces about 0.8MW of heating power. In the reaction tower RR _A <3A>Is withdrawn overhead as a vaporous methanol-water stream S _AB <3A03>. Via a condenser K _RRA <3A05>Recycling a portion of this stream to the reaction column RR _A <3A>And the remaining part (64.4 t/h) is supplied to the first rectification column RD ₁ <1>. At p is ₁ ＝～Operating the rectification column RD at 1.1 bar ₁ <1>. In the rectifying column RD ₁ <1>Is supplied with a liquid fresh methanol stream S of 9.5t/h _XE1 <205>(rectification column RD in FIG. 4) ₂ <2>Shown at the top) and a vapor methanol stream S is withdrawn _RDB1 <101>。

Via a condenser K _RD1 <102>Will S _RDB1 <101>Is recycled in part to column RD ₁ <1>In (1). Will S _RDB1 <101>Is in the compressor VD ₁₃ <16>Medium compressed to 2 bar and supplied to reaction column RR _A <3A>Where about 1.2MW of compressor power is required. In the rectifying column RD ₁ <1>Liquid stream S of the water-methanol mixture discharged from the bottom of _RDS1 <103>Said stream S _RDS1 <103>S of 18.9t/h _RDS12 <104>Part of it is sent to a rectification column RD ₂ <2>And flow S _RDS1 <103>The remainder of (1) is regarded as S _RDS11 <105>Recycled to RD ₁ <1>In (1).

Discharged stream S _RDS12 <104>At the pump P<15>To 3.4 bar and this stream is fed to the second rectification column RD ₂ <2>. At a pressure p of 3.2 bar ₂ Lower operation of the rectification column RD ₂ <2>. In tower RD ₂ <2>Condenser K of _RD2 <203>I.e. simultaneously being tower RD ₁ <1>In the evaporator of (1), is a column RD ₁ <1>Heating power of about 6.3MW is provided. In the rectifying column RD ₂ <2>Taking off a stream S of vaporous methanol at the top _RDB2 <201>. Via a condenser K _RD2 <203>Will S _RDB2 <201>Is recycled to the column RD ₂ <2>In (1). Will S _RDB2 <201>The remaining part (15.2 t/h) of (A) is supplied to the reaction column RR _A <3A>. In the rectifying column RD ₂ <2>The bottom of the column discharges a liquid stream of 3.7t/h water (contaminated with 500ppmw of methanol). In the rectifying column RD ₂ <2>Evaporator VS _RD2 <204>Here, the use of heating steam introduces about 11.4MW of heating workAnd (4) rate.

Will be at RD ₁ <1>And RD ₂ <2>Is withdrawn overhead as a stream S of vaporous methanol _RDB1 <101>And S _RDB2 <201>Is mixed with the corresponding, non-recirculated portion and recirculated to the reaction column RR _A <3A>The bottom of (a).

In this embodiment, a total of about 12.2MW of heating power via heating steam and about 1.2MW of electric power (compressor power) are required and must be provided externally.

5.5 results

In the examples of the invention and not of the invention, a comparison of the proportions of heating steam and electric current required to meet the energy requirements shows that: the method of the invention surprisingly makes it possible to meet a large proportion of the energy demand by means of electrical energy and to minimize the proportion of power provided by heating the steam.

Claims

1. For preparing at least one compound of the formula M _A Process for the preparation of alkali metal alkoxides of OR, where R is C ₁ To C ₆ A hydrocarbyl radical, and wherein M _A Selected from sodium, potassium, wherein:

(a1) In the reaction rectifying tower RR _A At a pressure p _3A And temperature T _3A By passing a reactant stream S comprising ROH _AE1 And comprises M _A Reactant stream S of OH _AE2 Reacting in a counter-current manner to produce a catalyst comprising M _A OR, water, ROH, M _A Crude product RP of OH _A ，

Wherein in RR _A Is taken out of the lower end of the vessel and contains ROH and M _A Bottom product stream S of OR _AP And in RR _A Withdrawing a vapour stream S comprising water and ROH at the upper end thereof _AB ，

(a2) And optionally, simultaneously and spatially separately from step (a 1), in a reactive rectification column RR _B At a pressure p _3B And temperature T _3B By passing a reactant stream S comprising ROH _BE1 And comprises M _B Reactant stream S of OH _BE2 In a counter-current manner to produce a catalyst comprising M _B OR, water, ROH、M _B Crude product RP of OH _B Wherein M is _B Is selected from the group consisting of sodium and potassium,

wherein in RR _B Is taken out of the lower end of the vessel and contains ROH and M _B Bottom product stream S of OR _BP And in RR _B Withdrawing a vapour stream S comprising water and ROH at the upper end thereof _BB ，

(b) Subjecting said vapor stream S _AB And, if step (a 2) is carried out, the vapour stream S obtained _BB Is conveyed to a first rectifying tower RD ₁ In (2), the vapor stream S _BB And S _AB Mixed with or with S _AB The transfer is carried out separately from the other,

to be in said first rectifying column RD ₁ To obtain a mixture G comprising water and ROH _RD1 ，

(d) Passing said bottom stream S _RDS1 Is completely or partially sent to a second rectification column RD ₂ In the step (1), the first step,

(e) At a pressure p ₂ And temperature T ₂ Next, the mixture G is mixed _RD2 Separated to be in RD ₂ Comprises a vapor stream S of ROH _RDB2 And in RD ₂ A bottom stream S comprising water of the lower end of _RDS2 ，

Characterised in that p is ₁ >p ₂ ，p ₁ >p _3A And in the case where step (a 2) is performed, p ₁ >p _3B ，

And in that (f) will come from S _RDB1 To said second rectifying tower RD ₂ The mixture G of (1) _RD2 。

2. The method as set forth in claim 1, wherein,wherein in step (f), energy is directly transferred from S _RDB1 Is transmitted to G _RD2 。

3. The method according to claim 2, wherein at least one of steps (α -i), (α -ii), (α -iii) is performed:

(α -i) transfer energy from S _RDB1 To slave RD ₂ The bottom stream S discharged _RDS2 S of _RDS22 Part of, and then S _RDS22 Recycled to RD ₂ Performing the following steps;

(α -ii) will react with S _RDB2 And S comprising ROH and water _RDS2 Different at least one stream S _RDX2 From RD ₂ Discharging and then transferring energy from S _RDB1 Is transmitted to S _RDX2 And will S _RDX2 Recycled to RD ₂ Performing the following steps;

(α -iii) reacting S _RDB1 Transmitted through RD ₂ Thus transferring energy from S _RDB1 Is transmitted to G _RD2 。

4. The method of claim 1, wherein in step (f), energy is indirectly transferred from S _RDB1 Is transmitted to G _RD2 。

5. The method according to claim 4, wherein at least one of steps (β -i), (β -ii), (β -iii) is performed:

(beta-i) will be from RD ₂ The bottom stream S discharged _RDS2 S of _RDS22 Is partially recycled to the second rectification column RD ₂ Wherein energy is transferred from S _RDB1 To at least one of S and S _RDS22 Different heat transfer media W _i1 And then from the at least one heat transfer medium W _i1 Is transmitted to S _RDS22 And then S _RDS22 Recycled to RD ₂ Performing the following steps;

(beta-ii) reacting at least one with S _RDB2 And S comprising ROH and water _RDS2 Different flows S _RDX2 From RD ₂ Discharging and transferring energy from S _RDB1 To at least one of S and S _RDX2 Is different in thatHeat transfer medium W _ii1 And then from the at least one heat transfer medium W _ii1 Is transmitted to S _RDX2 And then S is _RDX2 Recycled to RD ₂ Performing the following steps;

6. The method of claim 5, wherein W _i1 、W _ii1 、W _iii1 Each of which is water.

7. The method of any one of claims 3, 5 and 6, wherein at RD ₂ Said vapor stream S of _RDB2 Taken out of the bottom of S _RDX2 。

8. The method according to any one of claims 1 to 7, wherein S _RDB2 At least partially used as the reactive distillation column RR _A Of (2) _AE1 And, if step (a 2) is carried out, can be used alternatively or additionally as the reactive distillation column RR _B Of (2) a reactant stream S _BE1 。

9. The method according to any one of claims 1 to 8, wherein S _RDB1 At least partially used as the reactive distillation column RR _A Of (2) a reactant stream S _AE1 And, if step (a 2) is carried out, can be used alternatively or additionally as the reactive distillation column RR _B Of (2) _BE1 。

10. The method according to any one of claims 1 to 9, wherein S comprising ROH is to be reacted with _AE1 And S _BE1 Different flows S _XE1 Is added into a rectifying tower RD ₁ And a rectifying tower RD ₂ RR of reaction rectifying tower _A And if step (a 2) is carried out, alternatively or additionally to the reactive rectification column RR _B In (1).

11. The method according to any one of claims 1 to 10, wherein R is methyl or ethyl.

12. The method according to any one of claims 1 to 11, wherein step (a 2) is performed.

13. The method according to any one of claims 1 to 12, wherein p is _3A >p ₂ And further in the case where step (a 2) is carried out, p _3B >p ₂ 。

14. The method according to any one of claims 1 to 13, wherein the bottom stream S _RDS2 Comprising water and ROH.

15. The process according to any one of claims 1 to 14, which is carried out continuously.